Author's Notes:
Thirteen and Ace. Inspired by That Line from The Halloween Apocalypse and probably soon to be jossed via THAT LINE! from the Centenary Special trailer.

Originally posted to AO3.

"That stuff's dangerous, Professor," says Ms McShane, known to her friends as Ace.

"I was in a pinch!" protests the Doctor.

Ace hms sternly. "How many times have I told you it's unstable?"

"I know what I'm doing! Ace, you know—"

"And the timers are unreliable," she continues inexorably.

"I know how to be careful."

"That's not what that friend of yours tells me," she replies. "Don't let me hear about you taking stupid risks again."

"Ace..." the Doctor grumbles.

"No more nitro-nine," says Ace firmly. "I've developed a much better formula now. Let me get you stocked up."