The episode starts In Medias Res, as the Doctor and Lucie fight an evil scientist named Dr. Zimmermann. Lucie has decided to take a few levels in Science Hero, and she's come up with a rather elegant plan to disrupt Zimmermann's gadgets. The Doctor gladly helps her with the implementation and compliments her new skills as they banter, flirt and run a lot. Zimmermann's planning to sell a time weapon to the highest bidder, even if it would mean the deaths of billions. The Doctor obviously doesn't approve, but they're interrupted anyway by hungry Clock Roaches (the Tar-Modowk).