A police officer checks in to a rowdy bachelorette party, where he claims he's there with a warrant to arrest Jamie Ruiz. The officer is dragged into the party. The next morning, Castle awakes to see (and hear) Alexis and Martha doing singing exercises. Alexis explains that she told Martha that maybe she wanted to try out for her school's production of Grease, and Martha wanted to help out. Big mistake. Castle gets called to a crime scene with Beckett and Lanie, and Lanie explains that the murder was initially an officer down call. When they examine the body, they discover that the victim isn't actually a cop, but is only dressed like one. He was a male stripper. After identifing the victim as Derek Brookner, they find the address of the party Derek performed at. The party is still going on, and Castle is mistaken for another stripper, but the women are brought in for questioning. Only one woman left the apartment right after the party: Camille Roberts. Derek had a restraining order against Camille, but when she is questioned, she says that she had a history with Derek and wasn't happy that her actor friend had turned to exotic dancing to make money. However, he did tell her that he thought that this change in career would kill him. Beckett doubts that Camille had anything to do with Derek's murder. Meanwhile, Esposito and Ryan sift through Derek's belongings, and discover his acting reel, which includes a turn on an America's Most Wanted-type show as a leader of a motorcycle gang. Derek's agent tells them that he hadn't gotten an acting job in more than a year. Lanie examines the body, explaining to Castle and Beckett that Derek had dyed his hair gray, probably for an audition. But there's also a single long, blond hair found on Derek which wasn't his. The hair was tested and found to have traces of steroids. Esposito and Ryan go to Derek's workplace (Mucho Men). Lloyd Sanders, owner of the company, thinks that the pair are there to audition and tells Esposito that he's already got too many A-Rods. Ryan, however, might make a good Edward Cullen and that there have been requests for the guy from Twilight. Lloyd explains that Derek was one of his best employees. Derek mostly did bachelorette and birthday parties, but he also danced at a club called The Package Store. And the mystery hair may have come from someone there, considering Lloyd knows most of the dancers at the club use steroids. Castle and Beckett go to the club, and Castle is first mistaken for a dancer until he tells the enraptured women that Beckett's his girlfriend. The bartender explains that Derek and another dancer named Hans had bad blood between them, because Hans was jealous of Derek getting the headlining gigs. Watching Hans dance on stage, they notice that he does have long, blond hair. Backstage, Castle and Beckett question Hans von Mannschaft. Hans explains that he was at the club at the time of the murder, so he had a lot of witnesses that night. All the dancers share a closet so his hair might have gotten on Derek's clothes from that. Hans also points out that Derek had a cougar who was in love with him, but they might have broken it off since she hadn't sent Derek any tokens of affection (like flowers) lately. Ryan and Esposito track down the florist who supplied the flowers, and they find out the girlfriend is Rebecca Dalton, a widow who was a former model. Meanwhile, Alexis and Martha are still rehearsing for Grease, and Alexis is up for the main role of Sandy. Castle admits that his mom's really bonding with Alexis, and Martha is stunned at the compliment. When Castle and Beckett go to talk with Rebecca, she already has her lawyer (Michael Grant) with her. Rebecca met Derek at a charity auction where he was hired to mingle and encourage guests to bid. She was attracted to him and they had a relationship for a while, but that went south when Derek asked her for $25,000 and he refused to give a reason why he needed the money. Rebecca wondered whether he was cheating on her, so she hired a private detective to track his every move. According to the photos, Derek had fallen in with some really bad people, like the real gang leader he portrayed on America's Most Dangerous Criminals, Billy Grimm. The episode Derek starred in helped capture Grimm, who was wanted for attempted murder. However, the victim refused to testify so Grimm was let go. He swore vengeance on everyone who wronged him, even the actor who portrayed him on TV. Castle and Beckett speak to Grimm, who claims he doesn't know anything about Derek's murder until Beckett threatens to have the police explore Grimm's motorcycle shop for stolen parts. Grimm says Derek brought him $25,000, but Beckett counters that with a photo of Derek with Grimm's girlfriend. She told Derek that Grimm would bury the hatchet if Derek gave him enough cash. Grimm thinks what his girlfriend did was very sweet, and he also has an alibi on the night Derek was murdered. The team tries to figure out how Derek could have raised the money so quickly, especially since his bank accounts never seemed to have more than a few thousand dollars in them. A name found in Derek's belongings, Jesse Mandolay, is the key. At first, it seemed like Derek borrowed the $25,000 from Jesse and then was killed when he couldn't pay back the loan, but it isn't that simple. Jesse turns out to be Derek himself. Clues in Derek's apartment and the fact that he dyed his hair gray leads Castle to think that maybe Derek had to play the role of a financial adviser. Trying to find people that "Jesse" worked with uncovers a woman named Bella Lombardo, who says that Jesse was selling luxury property at rock-bottom prices. The whole thing turned out to be a scam, however. Derek may have been hired to portray the public face of his company, while someone else raked in all the cash. The team finds out that Sunfire Limited, the supposed company that Jesse claimed to work for, is owned by Rebecca Dalton. Rebecca was strapped for cash after her husband's death, investing in a lot of businesses that eventually went under. Rebecca had no idea that Sunfire Limited was created, because it was made in her name by her lawyer, Michael Grant. He set up the fake company under her name and was also taking her money right out from under her. When Derek took $25,000 from the company's assets, Michael knew that their little scheme would be revealed and he killed Derek. Later, Castle and Martha are cooking together while they discuss the case. Alexis says that she didn't get the part, and Martha is devastated. However, Alexis did get the prime backstage role of stage manager, which she thinks suits her a lot more.