At 4:07am, a woman taking a break from unpacking to drink wine looks out the window and sees a sailor being strangled in an apartment across the street. She pulls out a video camera, but by the time she can turn it on, the people have disappeared. Later that morning DiNozzo arrives at work to find Kate scheduling a dentist appointment after canceling three times due to a dentist phobia. Gibbs arrives and sends McGee to interview the woman from earlier, with instructions to call if he finds anything. He meets a Metro police detective, who found no sign of a struggle in the apartment or any other witnesses, so he thinks the woman, named Erin Kendall, imagined things due to the mixture of late night and alcohol. He called NCIS since she was insistent that she saw a sailor murdered. When McGee arrives, she admits to having a few drinks, but assures him there was a man in Navy dress blues being strangled, though she has no way to prove it. McGee and Erin also discover while talking that they are both MIT graduates. Back at the bullpen, Gibbs asks Kate if she is keeping her dentist appointment, and DiNozzo suggests hypnotism. McGee then calls and tells Gibbs that there is something there, and to "roll Boss". When the team arrives at the apartment, rented by a tenant named Thorne, there's no obvious evidence to back Erin's story, but McGee's gut says she's telling the truth, so they search the scene, with Gibbs telling McGee that they wouldn't spend too long on the case. Back at Abby's lab, she runs off McGee after agreeing that Gibbs is probably testing him, and she finds a fingerprint in the apartment that belongs to a Petty Officer Dillon who didn't show up for work that morning. When they go back to the apartment, they find a hidden compartment in the sofa containing a gun and a separate empty box, which Abby figures out likely held money. Kate also figures out that the name Thorne was an alias. In the meantime, Metro police find the body of Petty Officer Dillon, who was strangled at around the same time as Erin saw the assault. While Abby is running ballistics on the gun in Thorne's apartment, Erin and McGee try to build a composite sketch without success, but are clearly hitting it off. Dillon's girlfriend said that he was coming into money soon, but didn't know how, and they suspect robbery was the motive. That night, as McGee is staying in Thorne's apartment in case Thorne comes back, he and Erin are having a personal chat when someone breaks into her place and strangles her as McGee watches from the window. McGee arrives there too late and is hit by a lamp as the killer escapes. While the team is the scene, Abby calls to say the gun from Thorne's apartment was used in 2 prior killings. The next morning, Kate comes back from the dentist after using hypnotism to get over her phobia, and suggests McGee try the same thing. While under hypnosis, McGee reveals that the killer was wearing a large watch on his right hand. Separately, Abby figures out that Petty Officer Dillon and Thorne was the same person, with Dillon using the alias while working as a professional killer on the side. McGee realizes that the apartment manager wore the same watch, and chases him down. He considers shooting him, but Gibbs stops McGee, and arrests him. Later that night, Kate and DiNozzo watch Gibbs tell McGee that he'd done a good job on something he had written, which turns out to be a sympathy note to Erin's parents.