Callen, Sam and the team investigate a top Naval Engineer’s murder and get unexpected help when Director Vance sends Abby to Los Angeles. Abby has a theory that a number of seemingly unconnected murders have been perpetrated by the same killer, someone she has dubbed the “Phantom” because he leaves behind no trace evidence. While Sam and Callen investigate their best suspect, the engineer’s bitter wife, Abby examines the crime scene. The ‘negative’ footprint at the scene gives Abby her best clue, the killer is wearing a special hazmat suit which picked up dust, leaving the footprint and explaining why there is no forensic evidence. While they’re waiting on information about the suit, Eric and Abby go out to a Hollywood Goth club, and everyone is stunned when Abby is kidnapped. The investigation quickly shifts to find Abby. Nate suspects the killer will keep Abby alive to gain her admiration for his “work” but time is limited. When the team find where the “Phantom” is keeping Abby, they must stage a daring rescue because they know he has booby-trapped his lair.