The one where the menace is spreading and Londoners are fleeing...
Picking up right from the end of last week's episode, in which the Doctor's evil double Salamander was sucked out of the TARDIS and into the void, this episode opens full-pelt. There's some great "hanging on" acting from Patrick Troughton and Deborah Watling, and Frazer Hines is particularly good at pretending he's clutching onto the TARDIS wall, then "falling" onto the console. What bothers me most about all this is how the Doctor doesn't seem at all bothered or regretful of the fact Salamander is, as he puts it, "floating around in time and space". Evil he may have been, but surely he didn't deserve that?
We're also treated to another of those marvellous scenes which are becoming a hallmark of Season 5, in which the Doctor expresses childlike glee and enthusiasm for the adventurous life he leads. Previously touched upon in The Tomb of the Cybermen ("Nobody in the universe can do what we're doing") and The Ice Warriors ("Let's go in!"), I adore how Troughton expresses the excitement of the Doctor's peripatetic existence. "I wonder where it'll be this time?" says Jamie, to which the Doctor - in beautifully lit close-up - replies: "Yes, I wonder!" The look on his face says it all. This is how Doctor Who should be - fun, carefree, exciting and surprising - and not the soap opera gloominess it sometimes became in the 21st century.