The Major Case Response Team investigates the scene of the apparent suicide of a JAG lawyer, Lt. Melissa Newhall, who by all appearances was happy and preparing for a wedding with her fiance.
Lt. Newhall's boss, Captain Bud Roberts, expresses his doubts that she killed herself, and reveals that she had once been threatened by someone recently released from jail.
This turns out to be a dead end, but the team discovers that Newhall led a double life as Rita, a woman enamored of violent sex with a large number of men.
Luckily, she was a dedicated diarist, even in her hidden life. Agent Sloane theorizes that Newhall was punishing herself and that something probably traumatic happened during her childhood.
Newhall's father reveals that the lieutenant had been troubled and difficult as a teenager. Her grief-stricken fiance helps them locate her diary from that time, and they discover the truth.
She and her best friend were at a high school where a predatory teacher sexually abused his students. The two girls took it upon themselves to teach him a lesson. Unfortunately, he died of a heart attack during their "lesson," and they buried his body in the woods.
Now, so many years later, his body had been found. Struck by overwhelming guilt over what they had done those years ago, Lt. Newhall committed suicide. Her friend turns over the suicide note to the NCIS team, though she faces potential charges in Pennsylvania.
Gibbs and Sloane leave to reveal their findings to Lt. Newhall's parents.