McGee returns to his apartment one night to find it being ransacked by two unknown men who also attack him. He kills one and wounds the other, who flees.
The man stole numerous items, including a drive that belongs to Delilah. McGee is worried about telling Delilah what happened at the apartment.
When they locate the wounded criminal, he says that his co-conspirator got a hot tip that there was something valuable in the apartment.
They track the "tip" back to the tenant who occupied the apartment before Tony DiNozzo, a criminal convicted of murdering and dismembering three people. He is of little help, but does indicate that there is, indeed, something worth finding in the apartment.
The team discovers a body under the floorboards, and Ducky discovers a key in the dead man's stomach. The dead man was a long-missing fugitive who stole a bunch of diamonds in a notorious heist. The diamonds are nowhere to be seen.
The dismemberer is not inclined to be of further help without special considerations, which Gibbs is not willing to give him. The team finds out on their own that the diamonds are located in a safety deposit box.
McGee finally confesses the whole sad story to Delilah, who reportedly takes it surprisingly well.