The one where nobody's quite as dead as they seem...
... Klieg fires his Cyber-gun at the Doctor, we hear a cry... but it's Callum who's been shot, not the Doctor! Phew! Luckily, Callum's only wounded, not dead, so he can sit out the rest of the episode clutching his arm with absolutely no lines to say (which is just as well considering Clive Merrison's awful American accent).
More importantly, what have the Cybermen done to poor Toberman? It looks like they've enacted some form of Cyber-conversion on him, but not a full conversion, not yet. Perhaps they're feeling a little tired because the Cyber-Controller packs them all back off to bed, ordering them to get back into their tomb cells to conserve energy. Which is a bit of a letdown, to be honest. And that's how episode 4 feels at times, a bit of a disappointment, because although it's got some lovely set pieces, it never really fulfills the potential you have for it in your imagination.