A would-be copper wire thief gets chased by dogs at a Mardi Gras storage facility and discovers the body of Petty Officer Jonathan Bell.
The team finds flowers and an engagement ring with him, suggesting that he was meeting his intended fiancee. They speak with Chief Petty Officer Phil Martino, who is filling in for Bell as aide to Admiral Hume. Martino is also an old friend of LaSalle. Admiral Hume tells them about Bell's girlfriend, Maria Garcia, but didn't know of any problems between Maria and Bell.
As it turned out, Bell was receiving online threats from a local man named Rodney Abbott, who claimed to be in a relationship with Maria Garcia. The team executes a search warrant at Abbott's house and find a wall full of pictures of Maria, plus a .45-caliber gun, the same type as the murder weapon.
Much to their surprise, however, Loretta reports that Bell was shot three times: twice with the .45 post mortem, with the killing shot coming from a 30-caliber rifle. Abbott confesses to shooting Bell's body but claims that Maria was going to refuse Bell's proposal.
Patton Plame and Sebastian work their cyber-magic to track down Maria Garcia, who has shut down all her social media accounts. They manage to track her phone, leading the team to another surprise: "Maria Garcia" is actually a ghost, a work of fiction created by hacker Marco Drayer off of bits stolen from the Internet.
They interview Drayer's old hacker boss to get leverage on Drayer, but before they can get much out of Drayer, he's killed by a roof-top sniper, who disappears before they can get up there.
Ballistics soon confirms that Drayer's shooter also killed Bell, and the team guesses that the shooter had been the one to hire Drayer to "catfish" Bell in the first place. Loretta's autopsy turns up a specific meal from a very expensive restaurant. Security footage reveals that Drayer ate with a blonde woman identified as Claudine Bouchard, a wanted international assassin. She had been taking care of loose ends before completing her mission.
They go to her motel room, but she's already gone.
The team realizes that she targeted Bell to gain access to Admiral Hume's schedule - Hume is part of an international anti-drug task force aimed at taking down major cartels, and their having a lunch meeting in the city. The team rushes to the restaurant and safely evacuates everyone. Brody and Pride take down Bouchard, but she falls on the trigger, blowing up the restaurant bare moments after LaSalle and his friend Martino run out the door.
Sebastian introduces the team to his girlfriend, proving conclusively that she is real, before going off to dinner with her. LaSalle tracks down his estranged brother's place of employment, but learns that he left without warning six months ago.