HHH5 - Colony in Space 5

This episode resolves one of the weaker cliffhangers in history, while setting up an equally tepid one at episode's end. At the end of Episode Four, The Master displayed a sudden thirst for gunplay, pulling a gun on The Doctor and threatening to kill him in cold blood purely so that the episode could end with some sort of (contrived) drama. Luckily for The Doctor, Ashe steps in at the right moment early in Episode Five, creating a moment awkward enough to warrant The Master to holster both his gun and his lust for blood.

Good thing, too, as just a few minutes later, The Master essentially beseeches The Doctor to help him (under the guise of holding Jo hostage and threatening to kill her) to gain entry into the ancient primitive city. At the gates of the city, The Master's TARDIS door alarm is triggered, and the episode ends as he is about to press a button on a remote control that will release poisonous gas and kill Jo. Yup, he's totally gonna press the button...and the last shot is of his finger slowly (and I mean slowly) descending towards the button. The question at the end isn't "Will The Doctor be able to stop The Master from pressing the button?", it's "Which elaborate Venusian aikido move will The Doctor choose when he inevitably stops The Master from pressing the button?"

One has to wonder - why did The Master bother with the whole Adjudicator business in the first place? Neither IMC or the colonists are interested in the ancient city. Only Ashe knows about it, but has never been inside. No one on the planet could have helped The Master get into the city, except The Doctor, whom The Master wouldn't have known would be there in the first place. The Master has had better plans in the past, that's for sure.