Teenage neighbors find the body of a Marine, LCpl. Korby, who apparently committed suicide by carbon monoxide; Gibbs and company investigate; Ducky promptly says that the death was not by suicide, and he soon sees irregularities. Ducky elaborates on his hypothesis against suicide, and Abby adds details. Korby was a practical joker whose pranks often displeased others; some of his tricks had caused problems within his outfit, and his fellow Marines had taken action. Tony consistently believes that Korby's wife killed him; he eventually starts to arrest her, but Gibbs stops him. Gibbs, Tony, and McGee put the right pieces together, and they bust the person responsible. Finally, Tony experiences a dental problem.
A Marine, a practical joker, dies, apparently by suicide by carbon monoxide; Gibbs and company investigate; Ducky rules out suicide, and Abby confirms. Tony starts to arrest the widow, but Gibbs stops him. The gang put the pieces together.
- It's nearly 1 a.m. and someone in a monkey mask is videotaping his friends as they TP someone's house for Halloween. They run for cover and wait to see what happens, but they notice a man's car in the driveway, with music blaring. They assume he's baked out of his mind, and then find a hose running from the exhaust pipe into the window. They open the door and a stiff falls out.
Tony strolls into work, setting the stakes for a bet with someone on the phone. They're playing "Larceny Lotto" -- everyone throws $200 into the kitty and tries to guess the number of disturbance calls on Mischief Night and Halloween.
Gibbs rounds them up for the scene of Lance Corporal James Corby.
On the scene, Duckie immediately says it's not a suicide - his skin's the wrong color for carbon monoxide poisoning.
Tony and Ziva interview the kids who found him, who call Corby a master prankster.
Cranky neighbor Ted Rogers stops by to complain about Corby - and the fact the kids TP'd his house.
Corby's garage is stocked full of Halloween props and shows signs of a fight. Outside, Duckie and Palmer try to move the rigid Corby - but he makes crackling noises when they move him, like he's brittle. Duckie plucks something from Corby's throat - a piece of his throat, frozen solid. The cause of death is liquid nitrogen.
Back at the office they see Corby was bumped back in rank for dereliction of duty. He has a super hot wife, which leads Tony to think she did it. Ziva reports she was at a spa in Virginia Beach, which Tony also finds weird since he just got back from the Middle East.
Sarah Corby say they had a deal - he'd work on his Halloween projects and she'd go to spa. She says she didn't want to go this year since he'd just gotten back. Her teenage step daughter Rachel is there, too. Her mom is dead and Sarah married her dad five years ago, but he was killed in Iraq.
In the morgue, Duckie calls out Palmer for finding Corby's method of death a little too "cool." Duckie has a demonstration of liquid nitrogen prepared for Gibbs. They use a pumpkin as a "stomach stand-in." Mist (steam? condensation? fog? who paid attention in chemistry?) pours out as Palmer puts the pumpkin top back on.
Duckie says Corby had previous scarring in his throat. Palmer drops the pumpkin and it shatters on the floor.
Ziva and McGee watch the kids' prank video as Tony has Sarah's file sent over. McGee tries to explain the joy of a prank to Ziva. Gibbs brings the team apple cider for Halloween.
Ted Rogers has filed the most complaints against Corby. Tony and Ziva go to his house. He's just starting trading from home on the Asian commodities market. He says Corby has put shaving cream in his mailbox and food coloring in his pool. "So, Mr. Rogers, did you kill your neighbor?" Tony asks.
Rogers says he was on-line his with Shanghai office during the murder. Twin ballerinas trick or treat at his door, he gives them energy drinks.
Gibbs visits Abby who's surrounded by Corby's Halloween props. She's found a car on the prank video, but can't get a plate. She did get a livery vehicle number, from the Quantico Marine pool.
And, his stomach sample had paint thinner in it from two months ago, when he was in Afghanistan.
Tony has found Sarah Corby was married three times, all to Marines who died leaving big life insurance policies. Ziva reads the files and notes the first two died in the line of duty.
The car they're looking for is still missing.
The report on Corby's latest mission hasn't been declassified yet. Ziva and Gibbs meet with Corby's squad leader, Barnes, who gave him a bad review, in part because of his practical jokes. He remembers Corby was sick a few days overseas. He says Corby had a falling out with Private David Singer.
Gibbs and Tony visit Singer on base. He says he was in Norfolk when Corby was killed. He tells them about Corby Saran wrapping guys in their cots in the middle of war. He says an old high school friend can provide his alibi.
McGee has found problems with Corby's unit, including multiple transfer requests, complaints and they were deemed not combat ready twice. It started two months ago.
Duckie dissects Corby's lungs for Abby. Duckie found evidence Corby was beaten more than two months ago. Gibbs think he was beaten to teach him a lesson, a "Code Red" (see: "A Few Good Men"). Duckie thinks four people jumped him. Gibbs thinks his entire squad.
They've found six people from Corby's unit who were in town the night he was killed.
In the lab, Abby reports she's got teams looking for the item used to transport the nitrogen, but she doesn't know what it is. Palmer comes in to hear the results of the tests on the lungs. It showed traces of food. Palmer thinks the nitrogen was carried in something with food in it, like a thermos.
At Corby's house, Tony visits Corby's wife and step-daughter, who are cleaning up. Tony asks his wife if he ever mentioned getting beat up or poisoned overseas. Then he mentions her previous husbands' life insurance policies.
Private Singer drops by with flowers for Sarah. He says he and Corby had their issues, but he's sorry. Tony wonders if they know each other.
Back at the office, Tony is doubting the wife's guilt. McGee and Ziva have talked to the guys in Corby's unit, who denied the code red.
They have the sign out sheet from the base. Corby's squad leader Sgt. Barnes signed off the base the night of the murder. And the mission reports show Barnes was denied his promotion three months ago - before Corby was poisoned and the unit fell apart.
Ziva and Tony pick up Barnes.
Gibbs interviews Barnes, accusing him of poisoning Corby for costing him a promotion.
Barnes says he knew about the code red and poisoned Corby overseas for his own good -- his flak jacket caught fire one night and gave away their position. It was because of a faulty flare, but no one believed it. Barnes was trying to get Corby sent home so he put a drop of paint thinner in Corby's coffee. But the unit found out what he'd done and lost respect for their leader.
Barnes produces a strip club receipt as an alibi for the night of the murder.
McGee says the alibi checks out. Tony's still clinging to the wife theory.
McGee finds a charge on Singer's card for champagne and caviar at the same hotel Sarah Corby was staying at.
Tony brings in Singer. They know he checked out the car. He doesn't say anything to Tony's accusations, so Tony thinks he's covering for Sarah.
As they pause the interview to sum up the case for the viewers' benefit, McGee says he found a charge on Sarah's card for a garden hose and roll of duct tape. Ziva is indignant that Tony might be right about the wife after all.
Gibbs talks to Sarah Corby, beginning with her affair with Private Singer. They think he drove from the hotel to her house to kill Corby. But she says it was her, deciding she couldn't go through with cheating on her husband. She was dropped off by a car service at the hotel and borrowed Singer's car to drive home to confess to her husband. But she chickened out and just sat there then left. Tony starts to arrest her, but Gibbs leafs through the crime scene photos and calls him off.
Gibbs has McGee play the prank footage, focusing on a car on the street. It's Corby - which was found with him in the driveway.
Gibbs checks the car in the garage -- the seat is really far forward.
Gibbs and Tony confront Rachel, the step-daughter. They found the thermos at her friend's house. Everyone was too drunk at the party to remember her leaving. The clerk remembers her buying the hose and duct tape with her step-mom's card. She tried to frame Sarah.
They know she had a trust fund from her dad, which Sarah was supposed to control until Rachel was 25. She was trying to get Sarah sent away so she could access her money.
Rachel admits it, saying her step-mom went after anything in a uniform and used men and her step-dad acted like a juvenile delinquent. They arrest her.
McGee comes in to work and Ziva hands him some coffee, then waits. He sits at his keyboard and it starts to foam. Then Tony comes in -- high from winning the Larceny Lotto (he gave the money to charity). Ziva also gives him a drink, begging him to stop calling her "Probie." He takes a swig and likes it, cracking a huge grin. His mouth is blue.