Really, this episode was a treasure trove of ambient fascination -- if the plot was a straightforward ticking-clock, the environment was filled with teasing glances at the TARDIS. The Muscle brother tried stripping the console in the TARDIS' bridge, and overheard voices from the past. (I think I heard Amy Pond yell "We are in space!") Meanwhile, the Brains brother found his way to an Architectural Reconfiguration System -- "a machine that makes machines." He tried to take one of the glowing machine-making generators, and the TARDIS tried to stop him. First, it took away its door; then, it created a labyrinth, circling the travelers around endlessly. (ASIDE: I always enjoy the filmmaking of Doctor Who -- how the show manages to create whole worlds out of just a few sets -- and this episode marked a particular high point for the series, using a few corridors and sets to imply that the TARDIS was as big as your imagination. END OF ASIDE.)
The Muscle brother was attacked by a strange creature: Steam arose as the monster seemed to consume him. Meanwhile, the Doctor, the android, and the Brains brother were chased by a similar creature -- except this creature, horrifically, seemed to be two creatures fused together, like the two Ron Silvers in Timecop.
Clara found her way to the bridge of the TARDIS. As it happened, so did the Doctor and the remaining salvage operators. Except it wasn't the same bridge. They were both echoes -- the TARDIS was trying to protect them now. The Doctor explained that it was like flicking a light switch -- they were only together for a quick second. He managed to bring Clara over to their bridge, right before a creature attacked her. (Or so she thought…dot dot dot.)
Clara was not happy. "Why have you got zombie creatures?" she asked. "Good guys don't have zombie creatures. Rule one, basic storytelling!" Now that Clara was back in good hands, the Doctor felt safe telling the salvage boys that, in fact, the TARDIS was not going to self-destruct. "There is no self-destruct!" he said happily. "I used the old wiggly-button trick!" The engine was in no danger of overloading, and to prove it, he showed them a readout of the engine -- which, turns out, was very much in danger of overloading.
There was nothing for it: They had to go to the center (or, if you prefer, centre) of the TARDIS to fix things. Along the way, Clara noticed something curious: Other Claras, walking around and talking. The Doctor informed her that these were time echoes: "The TARDIS is leaking the past." (ASIDE: Weirdly, this is the second week in a row when Clara has seen another Clara -- last week, it was the TARDIS' hologram system. Are these purposeful echoes of Clara's three-people-throughout-time existence? Or is the show just playing with that idea? Are we building to an episode which will just be, like, a million different Claras talking to each other? END OF ASIDE.)
NEXT: The littlest Van Baalen Brother