The Invisible Enemy

Region 1

Region 2
VHS Video
(Doctor Who Story No. 93, starring Tom Baker)
  • written by Bob Baker & Dave Martin
  • directed by Derrick Goodwin
  • produced by Graham Williams
  • music by Dudley Simpson
  • 4 episodes @ 25 minutes each
Story: A mysterious infection begins sweeping across the pioneer colonies in the Solar System around the year 5000, malevolently forcing its victims to do its bidding. The Doctor and Leela race to discover a cure before the Swarm take over completely, aided by a robot dog named K9 and the facilities and personnel of an asteroid hospital, but the Doctor soon finds himself in the greatest danger of all....

DVD Extras include:

  • Audio commentary by Louise Jameson (Leela), John Leeson (Voices of K9 and the Nucleus), co-writer Bob Baker, and
    visual effects design assistant Mat Irvine.
  • "Dreams and Fantasy" making-of featurette (20 min.), adding director Derrick Goodwin, visual effects & K9 designer Tony Harding,
    K9 operator Nigel Brackley, and journalist Gary Gillatt.
  • "Visual Effect" featurette (16 min.) with miniature crew Ian Scoones and Mat Irvine.
  • Optional new CGI Effects
  • Raw studio footage (20 min.)
  • Photo Gallery music & sound effects montage (5 min.)
  • Pop-up Production Note Subtitles
  • K9 introductory guest spot on Blue Peter (4 min.)
  • bundled with "K9 and Company: A Girl's Best Friend" - the 50 minute season 19 spinoff pilot, and all its extras....

In-Depth Analysis Review

by Martin Izsak

WARNING: This review contains "SPOILERS", and is intended for those who have already seen the program. To avoid the spoilers, read the Buyers' Guide version instead.

"Doctor Who" finally sheds a good deal of its horror trappings and awakens to its science fiction potential with this story. Although mental possession and cold murder are still unfortunate centre-pieces to the story, the on-screen focus is solidly on exploration of the macro- and micro-worlds on which it is taking place, how and why it is happening, and how our heroes can stop it (instead of dwelling on the fear of it). It is also most refreshing to see a production that is so visually ambitious. A great deal of wonderful effects are successfully achieved, although lack of time also took its toll on others that didn't get pulled off so well. And though it may not realize it, it is also a wonderful complement to the next story, with one of its major settings being on the asteroid remains of the fifth planet: Maldek.


"The Invisible Enemy" begins with a good deal of impressive model effects work, as Ian Scoones works his magic and takes us to new worlds. Sometimes you can spot some wobble in the shuttlecraft, eating away at the illusion of scale, but the sequences are generally quite convincing and atmospheric. Gerry Anderson, eat your heart out.

Barry Newbery, a veteran set designer since the second episode of Doctor Who in its black-and-white inception, was also responsible for last year's dark secondary console room. He returns to get it right this time, and manages to create the most definitive console room in Doctor Who's long existence. With minor additions, the console room debuting here in "The Invisible Enemy" will remain in frequent use through to season 22, and continue to last and be seen less frequently up until seasons 25 and 26. The white walls with yellow roundels and swinging jagged-edge main doors at camera-left harken back to the earliest days of the program, while the superior realization of the scanner screen from last year is updated to a white colour that fits in with the new room, now shifted over to camera-right where it belongs. We also get a perfect little door leading to the rest of the maze-like interior, and the good old console is back, with its center column rising and falling and three central red tubes of lights flashing within. This is what it should be - the classic interior. It is such a grand relief to return to it.

"Invisible Enemy" deserved a larger slice of the season's budget if for no other reason than to get this set right, because all subsequent stories will benefit from it. The one noticeable element that could be improved on is that only half of the corner-joins between wall panels are properly hidden behind corrugated pillars, the others have their bolted-on angle-brackets exposed to the cameras, making it look a little too much like a set. Ah well, there's always room for improvement; at least the basic design is on form from now on. Philip Hinchcliffe sought so hard to get the Doctor away from UNIT and into space; if only he'd made the effort to get this room right, he could have been there much more successfully. Without UNIT HQ, the series needs this room as its standing centrepiece set.

Illiterate Flight

The police box exterior of the TARDIS also gets its due, making several proper materializations and dematerializations throughout the story, while the relationship between interior and exterior is adequately demonstrated as well. From a story point of view, however, one of the TARDIS's most interesting trips would be the one supposedly piloted by Leela when the Doctor is incapacitated. I'm not prepared to believe it unless I see it, and even then it would be a leap of character logic. As believably tense as episode two's reprisal scenes on Titan are acted out, the Doctor's final inward retreat should really happen in the console room after he's set the controls, to avoid the ridiculousness of having the temperamental machine piloted with such outstanding accuracy by a character who is only just learning to write her own name. That said, we need two more things for visual literacy to be complete - a proper police box materialization effect on the asteroid hospital (the footage for which is already in the can), and enough of a close up of the Doctor on the stretcher that we recognize him. As it stands, without seeing the attendants take him out of the TARDIS, or much of the TARDIS or Leela or Lowe in the opening stretcher sequence to begin with, I thought at first that the patient being wheeled around and into a mysterious horizontal compartment was just some unimportant establishing activity for the hospital before the arrival of our protagonists, until Leela's exchange with the receptionist, at which point realization dawned that I had missed something. This is one of the story's most confusing and disappointing sequences.

Set design on the rest of the story is good on the whole. The white of the hospital interior seems to use many elements similar to the TARDIS interior, but remains recognizably different. The white is contrasted by sets like those for the Titan base, which incorporate the orange-brown of natural rock and many dark areas, not to mention much of the interior of the Doctor's mind and the shuttle interior. The shuttle interior is another set where the multi-level aspect seems gratuitous, not arranged in a fashion that would help the crew relate to each other and see and do everything their duty requires.


As in most good science fiction, the story and plot has got to hold everything together, and Bob Baker and Dave Martin know their genre. A simple line of logical character motivation keeps our protagonists active as they go from location to location, dealing with one sci-fi concept after another, finding solutions to all their challenges. From exploring space to laser fights and mental battles to robot dogs to pseudo-cloning to "Fantastic Voyage" style surgery to medical research and immunology, this story does justice to it all.

Dialogue is another matter, for although Baker and Martin are capable of first-rate stuff, and have a knack for giving the Doctor some of his best, most in-character lines, they often resort to gimmicks as well. Last time, their catch-phrase crutch was "Eldrad must live." This time it's "Contact has been made." This is not too bad, actually, as it adds clarity to one of the story's unique key processes, and doesn't become a source of additional bad jokes. Dialogue concerning Leela's character is the script's weakest point, from the constant referral to her as "the reject" to all the derogatory comments on her intelligence. Think about it: although she comes from a non-technological warrior culture, she is actually one of the sharpest members of her tribe. She questioned her own traditions, and eagerly soaks up new knowledge and ideas. Travel is broadening her mind even further. She just has quite a ways to go yet before piloting the TARDIS becomes something the Doctor would believably attempt to teach her. Her morals and manners may still be lacking, but I don't think there's any dysfunction at all in her intelligence, particularly on a biological level capable of bothering the swarm. Her immunity is an important contribution to the story, but explaining it away as a lack of intelligence reflects more on the perceptions of the writers than on Leela herself.

Fantastic Homage

Episode Three gives us something never seen before or since in any Doctor Who story. Drawing inspiration from the feature film "Fantastic Voyage", its concept is taken a step further as the Doctor takes a trip inside himself, proving that this show can and will take its viewers anywhere. Wonderful stuff. A lot of marvellous effects are pulled off to achieve this environment, and the lining up of CSO backgrounds with the actors' feet is particularly top notch. This is one aspect of the finished story that the production team can be particularly proud of. Later biological visuals appearing on the equipment in Marius's lab are equally impressive, and do their fair share of helping the story along visually.

Guest characters for this story don't require too much of an acting stretch, as it is much more an action oriented piece, but the production is still blessed by the returning presences of Michael Sheard and Frederick Jaeger, who both give solid, enjoyable performances. Jaeger's Professor Marius is notably memorable.


It is K9 who steals the show, however, adding his much welcome and inimitable presence to the program. He is still a bit rough around the edges, as the production team learns how to operate him and get him to do all his tricks properly before the camera. John Leeson, who also voices the Nucleus during this production, gets K9's voice spot on from the beginning and does a marvellous job of him.


The list of effects for this story also includes a lot of ambitious superimposed beams and flashes. The most well done of these are the flashes of "lightning" that accompany each transfer of infection, which are almost always perfectly lined up, adding a credibility to each of the actors who gets taken over. Many one-off flashes like the one accompanying the Doctor's impromptu connection of two ganglia within his own brain are also superbly done. K9's laser blasts are not yet up to standard, in look or in sound, but he does at least get a half-decent visual red beam and a sound effect that matches the visuals fairly well. His very first shot embarrassingly seems to hit his assailant in the groin, until the man in pain grabs his knee instead. Ooops.

Perhaps the most disappointing beam effect is the one most used in the story - that of regular hand weapon fire. In theory, the red diamond flashing on the beams' targets beats many of the simplistic blobs of the late Jon Pertwee era and early Hinchcliffe era, without outdoing the outstanding white-star effects of "The Deadly Assassin" (story no. 88). But directors of those past stories were usually much better at getting literately clear footage to go behind the effect. In this story, there are too many beam effects shots needed, and not enough time for the director and his crew to line them all up properly. The corridor battles are the worst for this, in large part because they were the last segments taped for the story and suffered from the fact that time had run right out on the production schedule. The camera script went out the window, as a mad dash ensued to rush through and get some version of all the remaining required scenes into the can. Very disorganized, and it shows, but better than not completing the story, as "Shada" (story no. 109) will attest to some two years later.

Anyway, one is left to look at red diamonds flashing all over the place in these sequences, having little to do with the lines of fire they were intended to represent, while the cast shake their flat-nosed handguns at each other clumsily with appallingly uncareful aim. As much of a superimposition advocate as I am, I'm prepared to say that flash-charge props à la "The Monster of Peladon" (story no. 73) or "Planet of Evil" (story no. 81), without the red diamonds, would probably have provided a more effective result, but who knew in advance how desperately far behind schedule things would get?

Things fare a bit better as the action moves to the hospital reception area and back to Titan base for the conclusion, as these sequences were taped earlier when the crew still had time to do things right. The K9 prop is perhaps a little more out of control during this phase, but with a little tow from the Doctor's scarf, which doesn't seem too much a strain on credulity, he does all right in the end. It seems a bit silly for Leela and K9 to run out of ammunition so soon after landing on Titan, but then again, K9 was designed as a medical research aid, not a soldier, something easily forgotten in view of his role in later Doctor Who adventures.

Contact Has Been Gargled

This is not a story where the villain shines strongly. The Nucleus is at its best in the first three episodes, and works very well as a disembodied voice. But in the final episode, it is scripted with unreasonable impatience and the kind of insults and threats that make so many Doctor Who villains boring on the page. While the Nucleus looks dark and mysterious and effective inside the Doctor's mind, and even manages to have a nice philosophical exchange with the Doctor's clone, he really does suffer in the final episode, looking rather helpless and sounding worse and worse. The processed gargling and breathing noises he adds to the final climactic moments leave a bad after-taste on the story's action, as does the Doctor's inability to cure Lowe and Safran, rescue them from the violent pyrotechnics of the climax, and return them safely to the asteroid hospital. Luckily, the story ends on a happier note, with a nicely done scene of K9 joining the TARDIS crew, reminding viewers of the Doctor's success at completely curing Marius. At least he helped some of the people some of the time in this one. This helps create a better lasting impression of the story as it ends.

New CGI Effects

The DVD release of this story offers viewers the option of watching the story with many original effects replaced by upgraded ones, all without interrupting the pace of the original edit or the audio track. As always, options are cool. Two basic categories of effects have been upgraded. Pretty much all superimposed laser beams and flashes have been upgraded, and I can say that the results are consistently an improvement over the original. The corridor battles can be taken much more seriously now. Once in a while, it feels like too much of a glow has been plastered over the picture, but in the case of this story, it's usually covering up some embarrassment of camera blocking or lack of rehearsal, and thus is still an improvement. Even a pre-cut section of wall, which previously was too obvious, has been digitally corrected. Nice!

The other category of upgraded effects includes most, but not all, of the model work in the story. Nicely, the new material can intercut easily with the old, since the spacecraft was fashioned to look identical in both versions. But it's a bit hit and miss as to whether the new shots are better or more satisfying than the old. Let's dissect a sequence or two for an idea of what I mean....

The opening sequence:

  1. Shot 1: starscape. The old one is beautiful. The new one is beautiful. Take your pick. I think I'll favour the old one.
  2. Shot 2: Spacecraft left to right through asteroid belt. The old shot reveals embarrassing wobble. The new one is nice and clean. I'll prefer the new one here.
  3. Shot 3: Spacecraft approaching camera. The new shot looks like it was faked with a digital zoom to provide motion. I much prefer the original shot, since the motion looked more real, and there was really nothing wrong with it.
  4. Shot 4: Asteroids fly towards camera as we exit the belt. On the old shot, we see no starfield upon coming out of the belt. The new shot fixes this, and looks as though its asteroids are merely those of the old shot flipped around 180 degrees. I'll have the new one here.
  5. Shot 5: Actors in studio. Identical both ways.
  6. Shot 6: View of passing starscape through cockpit. The old shot has an embarrassing wobble. The new shot is a better starscape with smooth motion. I'll have the new one.

Titan Approach sequence:

  1. Shot 1: Craters of Titan rotate below spacecraft, with Saturn in the background. I love the old shot, each element is clear, and the frame is artistically composed. The new shot shows a dot descending to a bland haze on the bottom of the screen, while a corner of Saturn sits in the top corner. The old shot definitely rules!
  2. Shot 2: Pan across base on Titan's surface, as spacecraft approaches. Care has been taken to make the base look very similar, but the new shot loses the rotating satellite dishes that added life to the old shot. If there was anything I didn't like about the old shot, it was that the spacecraft seems to overshoot the base - but maybe that's to be expected considering the state of the pilot. My preference is the old shot.
  3. Shot 3: The pilot's hands operate controls. Identical both versions.
  4. Shot 4: Close up of spacecraft underbelly as it turns for landing. Truthfully, neither shot is great, or particularly bad.
  5. Shot 5: Side view of spacecraft landing on pad in front of base. This is a case where the old air-canister-blowing-dust trick paid off in giving the shot a sense of reality. The CGI shot attempts to composite these elements in, and it looks so much more fake. I'll have the old shot, which then means we should have the old version of the previous shot as well to match.
  6. Shot 6: Top view of spacecraft on pad, descending below Titan's surface. At this point, both versions use the old shot, and it cuts beautifully into both versions. The rest of this sequence is one of the few examples of old model work being retained for the CGI upgraded version of the story.

Really, I think a lot of the model work was only upgraded because, in the time since this story was made, our science learned a few things about the atmosphere of Saturn's biggest moon, and someone thought "The Invisible Enemy" should be made more accurate. Me, I'd have left all those old cool shots as they were, and not half because, for all we know, Earthmen could have siphoned off the methane atmosphere for fuel by 5000 A.D. This is fiction, after all!

Anyway, for the opening sequence, my ultimate preference would be for a mix of the two versions, while for the Titan Approach sequence, my preference is for the old. The real frustration is that both are cool, and no matter which one I watch, I feel like I've missed something good and interesting.

There are of course a few categories of effects that remain as they were in the original, chiefly everything for the interior of the Doctor's mind, and all the picture-in-picture mixes on CSO monitor screens, including biological scans and such.

Add the CGI options to a lively audio commentary, an insightful making-of documentary, a unique featurette with Ian Scoones discussing his work on this and many other stories, behind the scenes footage, priceless reactions from real dogs meeting K9 on various clips from other shows, and you have here one of the better DVD packages in the Doctor Who line. This one comes highly recommended.

"The Invisible Enemy" marks a sometimes shaky innovative leap for the program's production and direction, while also being a solid sci-fi narrative and introducing a unique new popular companion to the program as well. Although sadly rough around the edges, in the end this is definitely one of the season's better offerings.

International Titles:

Magyar (Hungarian): "A láthatatlan ellenség"

Français (French): (L'ennemi invisible)

Русский (Russian): "Невидимый враг"

Español (Spanish): "El Enemigo Invisible"

This story is now on DVD and VHS video. Click on the Amazon symbol for the location nearest you for pricing and availability:

DVD NTSC Region 1
for the North American market:
in the U.S.
in Canada
DVD PAL Region 2
for the U.K.
VHS Video
NTSC for North America
PAL for the U.K.

part of the End of the Universe Collection
for the North American region

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Read the In-depth Analysis Review for the next story: "Image of the Fendahl"

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