Factual error: Davros comments that, between them, the Daleks are carrying half a megaton of explosives - in other words, roughly twenty-five times more explosive force than the Hiroshima or Nagasaki bombs. An explosion of that size should cause enormous destruction (vaporizing everything within roughly two kilometers), yet when the Doctor detonates them they explode with about as much power as a small stick of dynamite each.

Revealing: In episode one, when the Doctor and his companion hear rumbling and the ground moves beneath their feet, when they step away you can see that they are standing on different ground than before, and it's not shaking.

Deliberate "mistake": The shot of the alien spacecraft flying in the sky is the same in episode 4 as in episode 1, only it's reversed. The taking off and landing are the same too, except smoke and rubble have been added.

Revealing: When the Doctor and his companion are running past explosions in the sand, you can see the scrape marks from where the effects team covered up the holes containing the charges.

Revealing: Right after Davros yells "The Daleks will rule the universe," in Episode 3, one of the Dalek operators accidentally starts to lift the top off his Dalek before the scene ends.

Plot hole: In episode 4, watch what Romana does to Professor Kerensky's time machine in order to make it work. It is surprising that the time machine works at all, considering she is supposed to be in Paris at the time. Romana wires up the time machine to a British (i.e. 3-pin 240 volts) electric plug instead of a "continental" 3-pin 110 volt plug.

Revealing: In episode 2, when Scaroth locks the Doctor, Romana and Duggan in the basement dungeon, and Duggan lights the lamp, notice that Tom Baker is standing between that lamp and the actual stage light used to brighten the scene. So, as the lamp is lit in front of him, Tom Baker's BACK (and not his front) glows bright under the increased illumination.

Plot hole: The sketch of Romana is different when it's seen outside the café from the one seen inside the cafe (and just who's doing the sketch, and why?).

Revealing: In episode one, Scaroth's 'Jagaroth skin' on his wrist flaps about. Either that's a badly fitting piece of costume...or he's suffering from severely peeling skin.

Other: During John Cleese's cameo appearance at the end of episode 4, watch closely as the Doctor (Tom Baker) walks past Cleese; the Doctor throws his scarf behind him and hits Lalla Ward in the face with it.

Plot hole: The Atlantic Ocean didn't exist in Early Devonian times (c.400 million years ago), so Scaroth's ship could not have been where the Doctor claimed. The Atlantic was formed when Europe and Africa separated from North America around 160 million years ago and is still growing. What is now the sea-bed was once covered up by several miles of Continental Shelf. The Early Devonian landscape would have been far from barren as plantlife was well established by then. So, either the Doctor's theory that Scaroth's exploding ship caused the creation of life on Earth is wrong, or it was much earlier than he said.

Continuity: When the Count's henchmen come into the cafe to get the Doctor, Romana and Duggan, they usher them all out at gunpoint. When you see them in the location filming in Paris, Duggan's not there...but back at the Count's place (in the studio in London) he's reappeared.

Revealing: Before the TARDIS console explodes (as Erato is weaving his shell around the neutron star), Tom Baker casts a sharp look over his right shoulder...no doubt looking to see if the ground was clear where he was due to fall.

Plot hole: The Doctor should not need a book on Tibetan as he already knows the language...he went to Tibet in the Season 11 story "Planet of the Spiders". (Of course, that was Jon Pertwee, the 3rd Doctor Who. Perhaps losing the mastery of the Tibetan language was a result the regeneration into Tom Baker...).

Revealing: Torvin, stunned by K9, turns before falling, as if looking for somewhere comfortable to land; and the guard who goes to attack K9 and Romana acts very strangely: he stops and curls up before K9's blast hits him, almost as if he knows what is going to happen next.

Plot hole: Just as the Doctor asks where the TARDIS has materialised, watch the control console wobble. However, isn't it strange that the hat-stand in the TARDIS console room remains upright thoughout...so why does the console wobble, and the hat stand not move in the slightest?

Revealing: In the very first shots of this Doctor Who story, it is obvious that the "Empress" Spaceliner is a model - you can even see the stick that holds the model in place.

Revealing: Geoffrey Hinsliff (playing Fisk) accidentally refers to Tryst as "Fisk" at one point.

Plot hole: When Della gets shot in the face in episode four, she clutches her stomach. (What is even more remarkable about this error is that this keeps happening over and over again: someone gets shot and falls to the ground, clutching their stomachs, regardless of where they have actually been shot. See the error in Season 14's 'The Deadly Assassin' for an example of the SAME error occurring).

Visible crew/equipment: In episode 2, as K-9 seals the wall panel, watch out for the hand which emerges to hold it in place.