In the wake of Frank Best's dismissal, Inspector Jarvis promotes a reluctant Oliver to Acting Staff Sergeant. Today is also the day 15 Division gets a new rookie, Duncan Moore - an infuriating, eager, and connected millennial. Andy is up for the challenge and convinces Oliver to make her Duncan's Training Officer. But she may have acted too quickly. When Andy and Duncan end up as the first responders on a messy downtown homicide at a pawnshop, Andy has to try to show Duncan the ropes, while preventing him from compromising the case, himself, and his fellow officers. Meanwhile, Sam's sister, Sarah, is ready to leave his bedside, but not until she gives Andy some harsh and cautionary words about what to expect in the long run with Sam.