Doctor Who "The Ark in Space - Part Two" (1975)

After a lonely romp through the space station in the previous episode, our TARDIS crew gets to meet some of the ark's inhabitants as the Doctor's repair work that saved their lives finally begins to bring the humans out of suspended animation. The Doctor and Harry are considered spies by Noah (Kenton Moore) once he is revived and the Doctor's words about an alien intruder go unheeded, that is until Noah starts to become one of them. Halfway through the serial and we're not really aware of what the alien menace is and what its intentions are. That's not to say nothing has been happening as this episode mostly concerns the Doctor gaining the trust of the crew of the ark and preventing the intruder from succeeding in whatever it is planning.

Despite the headway he makes with Med-Tech Vira (Wendy Williams), once Noah is awake he assumes our friends are saboteurs and is not willing to believe a word from any of them. At least Sarah Jane awakes in this episode and starts to play more of an active role in the serial. Her being sidelined probably suited a practical purpose. Ian Marter was brought onto the show as Harry Sullivan because it was originally envisioned to have an older Doctor, much like William Hartnell as the First Doctor, and a young male companion would be needed for the action scenes. Once Tom Baker was cast however he could perform those duties himself and Harry became a redundant character as since the Third Doctor era the Doctor has only utilized one companion. Marter is likable enough in the role and Harry's befuddled, babbling physician is still a wonderful addition to the crew and unfortunately it's the stories that needed tailoring to having two companions rather than having the role of one split between the two of them.

The true nature of the alien insects that the Doctor deduces is a horrifying one and is hurt by the poor prop of the dead queen colonizer. The creature looks completely unbelievable and the only saving grace is the Doctor's comparison of them to wasps. The creatures lay their eggs in a host so when the offspring hatch they have a ready source of food. First Tech Dune became that source of food and it's possible his knowledge of the ark's systems also became a part of the creature's race which makes them even more of a threat to the humans on the ark. The most terrifying aspect of the creatures in revealed in the cliffhanger, after coming into contact with slime from one of the larva, Noah begins to change into one of them.

Favorite moment: After being stunned by Noah, the Doctor awakens completing the sentence he started before Noah shot him. Starting off as a comical scene as the Doctor says Noah was rude to cut him off in mid-sentence, once the Doctor hears that Noah has gone to the solar stacks where the creatures are he rushes to save the man who almost just killed him. The Fourth Doctor continues in the mold of his predecessors and puts others before his own welfare when they are in danger even if those he plans to save are his enemies.