They escaped. Making them be punished by the law— that won't be enough. They have to hurt, and they have to never be able to hurt another person.

( MK tugs at her hood, eyeing the Doctor more suspiciously, now, something of a feral cat in how she moves. A very skittish feral cat, hunched and like its realising that being lured closer with food and kindness is still being lured. She glances at the timer. )

Get what you like. I should go now.