The prow of a rowboat drifts across the lake in Central Park. The lifeless body of a teenage boy lies in the boat. His shirt is covered in blood.
During breakfast at the Castle house, Martha prepares herself for an Introduction to Life Coaching class at the New School. Alexis asks Castle if he wants to be a chaperone on her upcoming class trip to Washington D.C. But Castle is wary of leaving Martha alone in the loft, especially after the last party she threw. "There were lime shards embedded in the walls." Castle gets a call. There's been a murder.
Castle and Beckett arrive at the Central Park crime scene to learn that the victim is Donny Kendall, 18, a senior at Redding Prep. According to Lanie, the lack of blood indicates he was shot elsewhere then dragged to the boat. Beckett asks Ryan and Esposito to organize a perimeter walk to see if they can locate the murder site. Beckett wonders why the teen was buried at sea as Castle quips that Vikings believed you needed a vessel to reach Valhalla -- along with booze, a good horse, and a sacrificial woman.
At the Kendall apartment, Castle and Beckett interview Donny's parents. The last time either of them saw Donny was when he left for school the day before. Apparently, Donny spent most nights eating out or at someone else's house. Mr. Kendall lost his job when Lehman Brothers went under last year and the changes it forced in the family lifestyle hit Donny rather hard.
Castle and Beckett speak with Redding Prep's headmaster, Chris Markum, who explains that when the Kendalls could no longer afford tuition, the school put Donny on scholarship. And though Donny was one of their brightest students, he had been having trouble lately. Markum has no clue as to why Donny would have been in Central Park at night, but suggests they talk to Donny's friends.
Castle and Beckett interview Donny's friends -- Romy, Max, Brandon, Amanda, and Spencer. The five claim they hung out with Donny after school, but that everyone went home around five. Beckett confides to the kids that she went to Yorke Prep and understands the need to protect your friends, but that the truth will eventually come out. The kids admit that Donny fell apart after his family lost their fortune, including supporting his drug habit by dealing in the park.
As they walk through Central Park, Beckett tells Castle that she never went to prep school. Castle's impressed with her chutzpah. At a park bench by a paved pathway, they meet Ryan, who points out a gelatinous pool of blood on the grass, where Donny was likely murdered. Castle figures if the shooter had been a drug dealer working that area, he returned later to move the body so the cops wouldn't pin the death on him.
At the precint, Esposito has a female witness who was walking her dog in the park when she heard a shot and saw a white guy fleeing the scene. After looking through a book of mug shots, she identifies the man as a known drug dealer named Kent Scoville.
In the interrogation room, Scoville confesses that he sold drugs to Donny the previous night. He then goes further to say he sold to Donny and to his friends.
At the prep school, the kids confess that they were in the park with Donny when he was shot. The tell Beckett and Castle that Donny was accosted by a drug dealer asking for a couple of hundred dollars. When Donny didn't have the cash, the dealer pulled out a gun and shot him. The kids ran off in panic. But they got a pretty good look at the guy, particularly Romy. In the lineup room, Romy points out Scoville as Donny's shooter.
The next morning, Alexis awakens to find Castle watching her. He asks if she's done drugs. She hasn't. In fact, she hasn't gotten into any trouble. As if to reassure him, she adds that if she ever got into trouble, her friends would bail her out. This gets Castle thinking.
At the precinct, Castle poses a question to Beckett and company -- why didn't Donny's friends just give him the money? But the cops think Scoville is the culprit. Why would the kids peg the wrong guy for Donny's murder? Simple, answers Castle, because one of the kids did it.
Castle and Beckett re-interview Scoville. He confides that Donny regularly sold drugs for him... as did the other kids as a goof. Scoville claims he was hanging out with his friends when he heard a shot, but he didn't see anything. Furthermore, he doesn't own a gun nor does he have any firearms convictions.
Beckett and Castle meet with Romy and her parents in their apartment. Beckett asks to see Romy's wallet. She pulls out several hundred dollar bills -- enough to pay the alleged drug dealer. Then Romy confesses to playing Russian Roulette with her friends and what they thought with an empty gun. But, somehow, a bullet was accidentally left in the gun. Romy tells them that Max shot Donny.
The pair head to Max's apartment, only to find he's out. His mother thinks he went to the park. Beckett gets a call -- the authorities have found Max dead in the park, the victim of an apparent suicide.
The next day, Castle wakes to find Alexis staring him. She confesses that she lied, that she recently jumped a turnstile in order to catch a train. But Castle isn't angry; he's relieved that this is the worst thing she's done. Alexis is so upset that she decides to ground herself for a week -- but only after the D.C. trip.
When Castle arrives at the precinct, Beckett is filling out paperwork that dismisses the homicide charges against Scoville. According to the ballistics, the same gun used to kill Donny was the one Max used on himself. Castle points out that having the presence of mind to move Donny's body after the shooting is more consistent with a cold-blooded killer. Would a cold-blooded killer suddenly feel guilty enough to commit suicide?
At the morgue, Lanie points to an abrasion on Max's right index finger, which implies that someone may have "helped" him pull the trigger. And considering Max had a blood alcohol level of 0.28, he may not even have been conscious. In other words, Max was murdered.
Beckett theorizes that someone must have wanted Donny dead, so while they were all playing Russian roulette, that person put a bullet in the gun without Max knowing it. Whoever did that is the real killer.
Beckett drills Spencer. It was his gun and his bullets. But Spencer says that when Max was killed he was at his father's club, The Century, with Brandon.
At the Redding Prep cafeteria, Brandon corroborates Spencer's story. He pulls out his cell phone and shows them a video of the group playing Russian Roulette. He explains that the friends took videos just for laughs and that their cell phones automatically synced up their videos. In the video, Beckett and Castle see Max shoot Donny.
Castle and Beckett head to the precinct's roof to catch some fresh air. Beckett thinks it was smart of Brandon to keep that video in his cell phone, which strikes a chord with Castle -- Why did the kids keep filming the game after the first few rounds? It's because they knew what was going to happen.
Amanda is questioned next. She vehemently denies knowing anything was going to happen that night to Donny. Furthermore, she admits that Donny broke up with her, but it was only because she had hooked up with Brandon. This sets off alarm bells. Castle asks Amanda if it was Brandon who told her to shoot the video that night. Surprised to realize this, she says that it was.
Castle and Beckett confront Brandon, telling him that Spencer has now admitted that he made up Brandon's alibi. But Brandon is unfazed. On the night of Max's murder, Brandon claims he was out for a walk, but since he knew they wouldn't believe it, he asked Spencer to cover for him. He challenges them to prove otherwise.
At the precinct, they discuss how they can prove Brandon and Max were together on the night of Max's death. Esposito jokingly bemoans the fact that Max didn't take a video of Brandon killing him. If he'd even been near him, notes Castle, their phones would have synced up. On hearing this, Beckett grabs Max's phone, checks its sync history and finds the proof they've been looking for.
Castle and Beckett confront Brandon. At first, he's adamant in his innocence, but he soon crumbles under the weight of the evidence. Ironically, if Brandon hadn't moved the body, they might never have figured it out.
The next morning as Alexis is packing for her trip, Castle shows up with a packed bag. He's decided to chaperone her trip after all, much to Alexis' delight.
As Martha rushes them along, the doorbell rings and Castle opens it to find a group of people. He suspects the worst, but Martha assures him that this is simply her "life coaching class." Taking her word for it, Castle and Alexis continue out. Then they hear the pop of a champagne bottle and the sound of cheers from inside the loft... Alexis grabs Castle and drags him down the hallway, as they head off on their trip.