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.
When Shelia hires ex-convicts in her bakery, Don starts to get worried about what the consequences could be for their family. Lina and Abby attempt to uncover what went wrong at a hazing of a recruitment academy in Chicago.
Abby and Lina investigate a complicated case involving the suicide of a police officer; Mackie and Abby's brothers plan a surprise party for Abby.
Abby and Lina are sent to investigate when a young girl is trampled during a brawl at a wedding; Don recognizes Mackie's new man as someone with a shady past.
Abby and Lina investigate a fellow Internal Affairs detective; Brody seeks advice on how best to woo Abby.
Abby and Lina investigate the erratic behavior of a crime scene photographer, which leads them to take over the investigation of a murdered model.
When a man collapses in front of her, Abby attempts to give him CPR; Donnie tries out for the SWAT team.
Abby and Lina investigate an officer who is accused of stalking his police psychiatrist; Richie's new partner challenges his loyalties and ethics; Abby's relationship heats up.
Abby and Lina investigate a stripper's murder and discover she was killed at a private cop clubhouse where Don is a member. Meanwhile, Richie learns about Brody and Abby.
A woman's corpse disappears from the coroner's office and turns up in a twisted Internet video. Abby and Lina search for the body to ensure that the murderer doesn't go free.
An ex-con accuses some police officers of harassment. Meanwhile, Abby is propositioned by the detective investigating Richie's shooting of a teen, and Sheila visits the mother of the boy Richie shot in an attempt to cope with her own grief.
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.
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.
