In a casino, people play poker in a private room; the waitress brings drinks and one of the players tips her. Another player gets his drink, but doesn't tip the waitress. Betting continues, with bets of $4,000; all but two of the players fold. Doyle 'Candyman' Pfeiffer tells Ronnie Litre that no matter what, he's going to win because he has two aces, and just as he's about to put all his chips in the pot, he begins to convulse.
Grissom stands in the casino and looks around, watching people play the slots and listening. He tells Warrick that the slots play a perfect harmony that makes people happy. They head for the private room, which is taped off as a crime scene. Brass tells them that Doyle Pfeiffer was healthy until he dropped dead; because of the high stakes poker game, they're treating it as a murder. Warrick and Grissom look at the cards; from outside the room, Ronnie Litre shouts that the pot is his, he would have won; the police hold him back.
In the desert, Catherine and Nick arrive at an abandonned air field and find the body of a UNLV student; the detective tells them that the air strip hasn't been used in years, and Catherine notes that it's the perfect place to dump a body.
At the hotel, Sara, Warrick, and Grissom process the scene; Brass talks to Ronnie Litre, who is still demanding the money from the pot, claiming that he won by forfeit. The team finds urine on one of the chair seats; Grissom notes that leaving the table during the game could be seen as a sign of weakness. Grissom comments that poker is how he financed his first body farm while in university; Warrick is impressed and surprised, not only that Grissom played poker, but that he sat at a table with other people.
Dr. Robbins tells Grissom that it wasn't a heart attack, but he's not ruling out a stroke; he notes that there are lines on Pfeiffer's nails, a blue line on his gums, and a milky secretion at the corners of his mouth, all of which indicate lead poisoning. An x-ray shows something that looks like a bullet in this thigh. Grissom watches the tape of the game, noting that everyone has a tell.
Sara gets the test results that show there was something in the victim's drinks - the same thing that was in eye-drops that Lita Gibbons was using during the game; tetrahydroxaline. Sara says that it would be perfect as a way to kill someone because it's odorless and tasteless. Grissom agrees, but points out that Lita was the last one to arrive at the table, and never left, and so had no opportunity to kill Pfeiffer.
Dr. Robbins examines the body found in the desert, and tells Catherine and Nick that there was one gun shot wound through the head, and the victim's eardrum was blown shortly before his death. Robbins also noted a gasoline smell on the victim's clothing and sent it to trace for analysis. There is bruising on the victim's chest that looks like a safety harness. Nick photographs the scene, and finds some skid marks on the runway, he tells Catherine that there were two cars there, and one of them skidded out into a spin while the other continued straight on. Catherine finds a sideview mirror from a car. They both decide that they're dealing with car racing. They go to a hotel on the strip where racers meet. They ask if the racers go out to the air field, and are told that they do when it rains, as it did last night. They note that some of the cars have harnesses similar to the bruises on the victim; all of the cars have sound systems that are louder than jackhammers. They find out that the cars are done by Michaelangelo.
Dr. Robbins does the autopsy on Mr. Pfeiffer to examine his brain. At the hotel, Brass and Grissom watch Lita Gibbons play poker, and win. They speak to her, and find out that she uses eye-drops because the smoke bothers her eyes. Grissom takes a closer look and notices that she wears one contact lens; she says that she has bad vision in her right eye. Grissom continues to look at her eyes, and notices that her one contact s tinted; he tells her that he'll need to take the contact, and her eye-drops.
Dr. Robbins has the brain; he tells Warrick that there's uncalurniation, swelling due to the lead, and the chemical in the eye-drops caused his blood pressure to spike, and that's what killed Pfeiffer.
Nick and Catherine go to see Michaelangelo to talk about racing; he doesn't race, he just does the mechanics on the cars, and identifies the car as one that he sold to Jay Spelder. He doesn't have the check that he received in payment for it. Catherine gets a call that the car has been found in the used car lot of the Masters brothers.
Grissom gets a glass the same colour as the contact lens, and uses it on cards to find the aces, which are marked, and show up when the blue glass is used. He realizes that Lita Gibbons was cheating. Sara gives him the test results from the autopsy; Lita's eye-drops don't contain zinc sulphate, which was in the eye-drops that were in the victim's drink, so she didn't kill him.
Warrick talks to the waitress at the casino, who tells him that even though Pfeiffer didn't tip her that night, he sometimes did, if he was in the right mood, and that's why she was paying so much attention to him. She admits to playing one player against the other, and says that it's the way that waitresses work. Grissom talks to the bartender, who tells Grissom that there's a standard procedure for ordering drinks: soda first, then mixed drinks, then beer. Grissom notes that there's no alcohol at the bar; it's all done by computer, and the alcohol is in pre-measured shots that the bartender can't tamper with. Warrick checks the waitress's purse and finds eye-drops.
Nick and Catherine go over the car; it's been cleaned, but Nick finds a bullet in the moulding over the windshield. There are no visible body fluids, but they spray the car with luminol and find that there was blood all over the front of the car, with a void in the pattern where the driver was, meaning that Spendler was driving the car when he was shot. They interview Mr. Masters, who tells them that opportunity knocked and he answered; he found the car, abandoned, and he and his brother took it, cleaned it up and put it up for sale. He admits moving the body out of the car and leaving it behind, saying that he didn't call it in because the police would have impounded the car, and the guy was already dead anyway. Catherine informs him that he's just admitted tampering with a crime scene and has him arrested. A detective tells them that he's found out that the other racer was Tony Del Negro. They talk to him, and he admits racing against Spendler; his father is there, and angry that they're harassing his son, commenting that when his wife died two years ago, he couldn't even get an officer to return his calls. Nick checks his car, and notes that there's new glass in the windows, and asks about that; Tony claims that loud music blew out the window. Nick comments that there's been a gun fired in the car, and Tony tells them that that's how the racers get hyped up before a race. Mr. Del Negro tells them to leave, and they promise that they'll be back with a warrant.
Grissom looks through the computer records of the drink orders; he finds that the waitress followed the protocol for ordering in the first five rounds, but changed the order in the sixth, ordering the mixed drink for Mr. Pfeiffer first, before the sodas. Brass questions her, and admits that she put eye-drops in his drink, saying that all the waitresses do it to customers who stiff them. She says that she was fed up with him never tipping her, and just wanted to give him a case of diarrhea, but didn't intend to kill him. Warrick comes in with the tox results, which show that Pfeiffer had massive amounts of lead in his system, more than can be accounted for from the bullet in his leg.
Nick gets the results from the bullet that he pulled from the car; the casing has been shattered and they won't be able to test it or match it to any bullets from the Del Negro's gun. However, there are shards of glass in the casing.
Grissom watches the tapes of the poker game, looking for where the murder took place. The team has themselves set up around the table the same way, acting out the game, but they can't figure out where all the lead came from, or how it got into Mr. Pfeiffer's body. Grissom munches chocolates, the way that Pfeiffer did, and then has an idea.
Catherine tells Nick that the main suspect in the death of Mrs. Del Negro was Jay Spendler, but he was released due to a lack of evidence. This gives them a motive for Tony to kill him. Nick test fires a bullet through two windows, and it picks up shards of glass, the same as the bullet that they found in Spendler's car. They go back out to the desert to see if someone driving a race car could fire a gun into another car; Nick is wearing a helmet that sets off sirens and lights when hit with a laser. He and Catherine race, and she shoots him, setting off the helmet.
In the lab, Grissom tests the chocolates that Mr. Pfeiffer was eating.
Catherine and Nick talk to Tony Del Negro; he tells them that Spendler killed his mother during a street race and didn't even stop; no witnesses came forward. He tells them that he was with his mother when it happened, but he didn't know who it was that was driving the car that hit her; he only found that out after he started racing himself. He tells them that he started racing in order to find out who the driver was, and once he started racing, it only took him an hour to find out that it was Spendler. So he put in his time and waited for an opportunity to kill him. He's unrepentant as he tells them, "He took my mother's life, so I took his."
Grissom tells the team that a lot of chocolate comes from West Africa, where leaded gas is still used in cars. The rain is very much like acid rain, and the lead in the rain soaks into the soil and is then transferred to the plants. Warrick comments that Pfeiffer was the Candyman, and it was his lucky charm ever since he won big 16 years ago. This explains how he got so much lead in his system; Grissom agrees, saying that the eye-drops triggered his death, but ultimately, it was death by chocolate.