Navy Petty Officer James Muldoon calls 911. He reports that he encountered a man who was assaulting Amy Harrison so he intervened. He says that when the man turned and attacked him with a knife, he shot and killed him.

Gibbs interviews Muldoon, who reiterates his story.

Abby's forensic evidence initially supports Muldoon's story.

The team determines that the dead man Mitchell Graft lives alone, has a record for DUI, drug trafficking and sexual assault.

Petty Officer Muldoon is a decorated hero.

Gibbs seems suspicious.

Delilah gives McGee information about where the petty officer was, prior to the shooting, that indicates he lied.

McGee reconstructs the shooting scene by using elements of his dinner, which infuriates Delilah.

Tony's on a date with Leah Ramsey, and he begins to have doubts about the petty officer's story. He talks the case over with Leah, who becomes bored.

Ducky tells Bishop that the body wasn't lying in the same position as he was shot. Also, he was shot an hour before the call to 911 was made.

Gibbs concludes the crime stage was staged.

Abby reveals that Harrison texted Muldoon that afternoon, and that she's been texting him for three months. They know each other.

Tony and Gibbs interrogate Muldoon but he sticks to his story and demands a lawyer be assigned to him.

Abby reveals that the DNA on the bullets belong to Harrison.

Bishop and Gibbs interrogate Harrison.

Harrison and the dead guy knew each other when he was a guard at her detention centre when she was imprisoned for drug trafficking as a teen.

Bishop theorizes that the dead man and Harrison were drug dealing partners, and that something happened to imperil their business relationship.

Harrison tells them that she wasn't imprisoned for dealing drugs. She got caught holding a bag of pot in her school locker. She tells Gibbs she wouldn't rat out the person who owned it, so she took the rap herself.

Harrison tells them that Mitchell (the dead guy) sexually assaulted her at the detention centre for eight months. She had pushed it out of her mind until she saw him at a gas station the day of his murder.

She followed him and hit him with her car.

She says he knew her immediately, and came to her car door, screaming. She says she got out of the car, and when he came toward her she fired the gun.

She says she called Muldoon, who agreed to stage the scene and make it look like he killed the man.

Gibbs tells Muldoon he's not pursuing charges against either of them for obstruction of evidence, and that Harrison has a good case for self defence.