Callen and Amanda's relationship has fallen apart. The story takes place four years from the end of Denial and back tracks, explaining the events that led to their separation.

A Marine recently returned from deployment, mysteriously murders his entire squad. What Gibbs and the team learns with the aids of a Navy Psychologist, sheds new light on the case. The LA team inherits the witness' protection after the suspect hires a hit man in order to silence the loose ends.

The team shares their favorite Halloween memories. Callen has never forgotten his and is shocked when he sees a young girl is the very same costume. He be-friend's the girls mother with the hopes of reliving the kiss that changed both of their lives.