Title Act of Prevention.
A time-traveling physician wants to prevent the serial killer cases she is enlisted on. She changes the timeline and has done so for years, but a detective stumbles upon her secret. Why she does this is known: Her brother's trauma and random acts of disappearance, but what's not known is where he goes or what he does. She lives to prevent a life of loneliness and looks for meaning, but what stares back at her is not herself.