DOCTOR: Too fast to chase and capture, too toxic to touch directly... It's a bit of a puzzle.

MABLI: It's gonna kill us all, isn't it.

DOCTOR: Oh, Mabli, you went there way too quick. I said a puzzle, not a death sentence. I mean, it's a bit of a challenge, and I can't quite see the solution yet, but that's life – or medicine. Patients present problems; you figure them out and come up with solutions. That's what this is: a problem to be diagnosed, medicine to be administered. You're a medic. I'm the Doctor.