Siberian

She looked up at the Doctor.  “William Manton?”

The Doctor nodded.

“How?  Why?”

“I don’t know what predicated it.  His daughter’s in our custody.  One of our failures.”

“He gave his daughter the formula?  Without the usual preparations and procedures?”

“I suppose he thought he was qualified to oversee all that.  Despite my strict instructions that staff weren’t to partake.  Or he had other motivations.  It could have been a gift from a father trying to buy his daughter’s affections.”

“Or her forgiveness,” Alexandria looked down at the glass eye, then back up to the Doctor.

The Doctor’s eyebrows were raised in uncharacteristic surprise.  “Did you see anything suspect?”

“No.  I only met his daughter twice, and it was brief, her father wasn’t around.  But I know the divorce between Professor Manton and his wife was pretty bad, as those things go.  He was angry, maybe did some things he regretted?”

The Doctor sighed.

“So that was him?”

“Almost certainly.  He gave his daughter one of our higher quality formulas, and she couldn’t handle it.  When he realized what he’d done, realized that he couldn’t hide it from us, he took one formula for himself and fled.  I didn’t know what it had done for him until tonight.  The resemblance between Siberian and Manton’s daughter is subtle, but it’s there, and the footage from Hero’s helmet-camera has been run through every facial recognition program I could find.”

Interlude 15 (Donation Bonus 3)