The Doctor (William Hartnell), along with his granddaughter Susan (Carole Ann Ford) and companions Ian and Barbara (William Russell and Jacqueline Hill) materialise on a strange island dominated by an immense tower that houses a computer capable of controlling the actions of everyone on the planet. By holding the TARDIS hostage in a force-field, the sole caretaker of the machine blackmails the time-travellers into combing the planet for the five missing electronic keys needed to make the computer active. Terry Nation's highly contrived six-part premise serves to launch five separate 'adventures' among the planet's various cultures, none of which are particularly interesting or well-done. The script suffers from the 'selective amnesia' that is common in sci-fi/fantasy series: no matter how strange preceding events were, characters are constantly being told that they are 'just imagining' some current strange event. There is no continuity between the cultures visited, each is simply devised to set up a different kind of puzzle to be solved before finding the 'key', the 'teleportation bracelets' that allow the searchers to instantly travel around the planet are conveniently unused at times, there are a number of errors in the story-line (for example, Barbara teleports moments before the others yet seems to have arrived days earlier), and the lengthy courtroom sequence in which Ian is tried for murder resorts to the simplistic gimmick of surprised characters starting to blurt out their guilt before catching themselves mid-sentence. Hartnell was taking a break from production, so the Doctor is absent from three of the 'adventures' and, although the companions do their best to carry the show (despite Susan coming across as hapless and easily terrified), his presence is missed. The sets are imaginative at times but a bit cheap looking and clearly the show's budget did not extend to re-takes as Hartnell noticeably stumbles over lines several times. Apparently the series was a last minute substitution, which may in part account for its disjointed structure and seemingly rushed production. All in all, a weak entry in the First Doctor's canon (especially when compared to 'The Dead Planet' or 'The Tenth Planet'). * score and comments pertain to whole series.