Chicago Internal Affairs detective Abby Kowalski investigates crimes in the department. In the opener, Abby, a beat cop, accepts a promotion to detective in Internal Affairs, which doesn't sit well with her family of cops.

Richie shoots a teenage boy in the line of duty. Meanwhile, Abby works with one of her heroes in a case involving a mob mole.

When Don's ex-partner Paul is investigated for the death of his wife, Abby and Lina look into how she really died, which may lead to Don's old cases being reopened.

Meanwhile, Lina worries if her partnership with Abby will change after the birth of her baby, and Abby's relationships with Danny and Brody heat up.