Factual error: Giuliano explains to Sarah that he thinks the world is round as though this were radical. But this was the common belief throughout the late Middle Ages. The argument was about how big the Earth was and the ignorance about the existence of a continent between Europe and Asia.

Factual error: Giuliano makes references to the invention of the telescope. Yet the invention of the telescope was at least a century after the events in the story and Galileo's experiments more than 50 years after that.

Factual error: The nuclear physics in the reactor scenes is laughably incorrect.

Visible crew/equipment: After Rokon's message in episode four, Eldra starts ranting and raving. A BBC camera can be seen in the doorway behind the Doctor and Sarah.

Revealing: At the climax, when the Doctor and Sarah are setting up the scarf trap, the Doctor bumps a rock, which wobbles.

Continuity: When Leela attacks the guard near the computer complex in episode three, his gun goes flying down the hall. But she then picks it up right next to his body.

Visible crew/equipment: When Leela runs into Toos' quarters (and finds D84 leaning over Toos), we see a low-angle shot of her entering the room. Look at the brief shots of her before and after D84's line, "Please do not throw hands at me," and you'll see the front of the camera that took that low-angle shot jutting out into the doorway behind her, before it slowly retreats out of vision.

Revealing: At the beginning of episode four, when the Doctor is surrounded by robots, we initially see SV7 with *blue* eyes. Clearly someone forgot to add the glowing red-eye CSO.

Continuity: The Doctor's scarf vanishes while he's detained in the crew's quarters.

Revealing: When the Doctor is trying to unlock Uvanov's cabin door, Leela goes to join him and grabs the edge of the metal railing, which bends badly and then goes back to its original shape.

Revealing: In Episode 3, when Dask is cutting the wires, the second explosion happens too early.

Revealing: Watch the scene where Uvanov sticks a Laserson probe into the head of one of the Vocs (V4) as it is strangling the Doctor. After he shoves the probe in, you can quite see the suit's helmet come away from the rest of the suit.

Revealing: Immediately after the Doctor stabs SV7 in the back of the head and the robot crashes to the floor, the next scene shows the fallen figure of SV7 in the background - breathing heavily, with his chest moving up and down.

Continuity: When Uvanov captures Leela he says she has killed three people, but he only knows Chub and Cass are dead. Then Poul tells him about Kerril.

Revealing: When the Doctor confronts D84, the robot is shown in profile as the Doctor forces it to speak. The movement of the actor's jaw is visible behind the mask.

Revealing: Watch really closely when Leela throws the knife at one of the robots. You can see the knife fall to the floor about a second after she throws it. Then, of course, the next shot shows the knife sticking out of the robot's chest. Guess Leela isn't quite as good a shot as we thought.

Revealing: When the Doctor and Leela are put in Uvanov's cabin to await questioning there is a shot of a robot listening to them in which you can see the actor's neck.

Revealing: When SV7 comes into Taren Capel's workshop, its usual eyes are missing - only black discs are visible (later in the scene, these are overlaid with the red speckled pattern to show the robot being reprogrammed).

Continuity: From time to time in episode four, the "frozen" robots on the command deck can be seen to wobble - the most noticeable is when SV7 is threatening Uvanov over the communicator.

Visible crew/equipment: In episode three, when Toos talks about the disposal of robots, a crewman can be seen behind her, toward the back of the set.