Police officer Danny Pelham is killed during a stakeout to catch armed robber Terry Mays. Pelham's partner Pete Bowers had taken his wife to a hotel, leaving Pelham alone in their car. Mays says that he saw someone shoot Pelham; witnesses corroborate his description of the killer. Briscoe and Curtis look into Pelham's girlfriend, fellow officer Marissa Hastings. Pelham's co-workers report that she'd physically assaulted him before and was always calling to check up on him. She is arrested when the detectives discover someone from her department, presumably Hastings herself, contacted Bowers' hotel to check that he'd be there.

But Hastings' story is that Pelham was the abuser. She repeatedly reported him to Internal Affairs, but no action was taken. Pelham didn't even care when her partner Steve Felton tried to warn him off. At trial she tells the court that Pelham frequently beat her and even hurt her children. She admits she stabbed him but says it was in self-defense. [=McCoy=]'s argument is that Hastings felt she had no choice but to kill him. She couldn't even get a restraining order without a police report.

Carmichael realizes that Felton mentioned Pelham abusing Hastings' children - even though she claimed no one knew about it. Around the time of the murder, Felton went out supposedly to go to a pharmacy. [=McCoy=] and Carmichael confront him with the knowledge that he was not at the pharmacy, and convince him that if he doesn't tell the truth, Hastings faces a long sentence for murder. Felton confesses he shot Pelham to protect Hastings and her children. He is sentenced to a minimum 15 years in jail.

!!Tropes present in this episode
* DoubleStandardAbuseFemaleOnMale: Averted. When Briscoe and Curtis are told that Hastings physically attacked Pelham, they take it seriously and treat her as the prime suspect.
* IfICantHaveYou: Pelham was abusive towards Hastings and even threatened to kill her if she left.
* OffingTheOffspring: A reference is made during the trial about an other police officer who had murdered his wife and their children before committing suicide.
* OutlivingOnesOffspring: After the arrest of Mays and deciding he didn't commit thus murder, the police talk to someone who talks about "the bastard that killed our son", so it would appear that both his parents are alive.
* PoliceAreUseless: At least IAB is when it comes to handling complaints of domestic abuse.
* TheReveal: Hastings's partner, officer Steve Felton, was the one who shot Pelham, as he could no longer stand by Pelham's abuse of his partner.
* WouldHurtAChild: Pelham was violent to Hastings' children as well as her.