They run around the ship for awhile, and Christina finally decides to use her ninja powers to get this crystal from their engine room, crowing, "The aristocracy survives for a reason!" and once again trumpeting her readiness for all contingencies. So the whole time she's clipping herself into her apparatus and putting her hair back, the Doctor's babbling, and he finally figures out what she's doing, and stresses because she's going to electrocute herself on their security grid -- emphasis on cute! -- so he sonics her wire, and she deactivates the security thing with a big shiny red button, and once she's hanging over the crystal, they realize that at least one of the beasts is sleeping in the engine room, so there's a seat-of-the-pants moment where it seems like the monster will eat her, bless him, but she gets pulled back up at the last second and electrocutes the thing in the security grid as she's being hauled back.
This impresses the Doctor no end, even though she calls him "Spaceman" and reminds him about Donna, which reminds him about Rose and Martha and Jack and all, Kylie Minogue and Jackson, so he gets sad and standoffish, and takes a moment to discuss with her about how he's an alien with a time machine before finding the stolen Cup of Athelstan, given to the first King of Britain as a coronation gift from Hywel, King of Wales, and nattering at her about being a thief. She thinks he's going to get obnoxious about it, but instead he goes all dreamy and points out that stealing is his lifestyle too, for example his time machine, which he stole from his people to begin with.
Then the beasts start moving around inside the ship, and they try to abandon it, but the flies attack one of the monsters and are dispatched despite being offered a home on Earth by Christina, which is another very Doctor/Companion move. They run around for four million years, and then make it to the bus, where psychic lady helpfully says all psychically, "Run run run run run!" And the Doctor clamps some things to some stuff, to the wheels, and keeps hanging up on Malcolm, who in the midst of much technobabble has discovered a way to close the wormhole, which UNIT's own Erisa wants him to do despite the Doctor almost having saved the bus, and Malcolm can't because he's in love with the Doctor, so he ends up of course with a gun in his face, and this look like, "Shit, I completely forgot I work for UNIT."