Comedian Michael Borland is performing stand-up comedy at The Comedy Hole, murdering the audience in a very uncomforable way. Another comedian, Dougie Max, is outside the back of the comedy club psyching himself before his act begins. Alan Sobel, the club owner checks his watch, waiting for Michael's bit to end. Dougie finishes psyching up while a waitress zips him up after finishing her job with him. He goes into the club and gives the patrons a high five on his way up the stage. Michael Borland finishes his act to a very silent crowd before introducing Dougie Max onto the stage to a very excited crowd. Dougie takes a swig of water and spits on a patron, saying "Hey kid, it's a cruel world! Ain't it great?" The audience applauds him as this is his signature mantra.
Later, Captain Jim Brass briefs CSIs Gil Grissom and Catherine Willows on the sudden death of Dougie Max. He suddenly collapsed during his bit and the people got confused about whether or not it was part of his routine until he didn't get up. Assistant Medical Examiner David Phillips is present at the scene, determining Dougie's cause of death. Dougie's eye pupils are found not to be dilated, no foam or discolorization found on his lips, which would be signs of drug overdose. Grissom noted that he does not remember comedians dying of natural causes. Dougie died with a clenched fist, a classic Levine's sign, indicating that Dougie died of cardiac arrest due to heart failure. Grissom asks to turn back on the stage lights, but finds nothing. When Catherine asked Grissom what he was looking for, Grissom replied "A punchline?" Brass chimes in, "Ba-dum-dum."
Brass questions the club staff about Dougie Max's sudden death. Alan remarked that he loved Dougie, who kept The Comedy Hole in business. He inked a sitcom deal and Alan had to pay him a hefty sum to have him perform once a year. Alan was visibly upset emotionally and financially when Dougie died and suggested adding historical props to promote the club. The bartender, Barry Yoder, suggested to Alan that he could be a stand-up act, but Alan refused. Alan also told Brass that Dougie started with hack material before catching a lucky break and never let anyone forget about it. He points Brass to the wall of comedians who perform regularly at The Comedy Hole for murder suspects.
Catherine begins processing the Green Room. She finds a coffee table and a party platter with a card for Dougie Max on the table. Catherine spots a suspicious white powdery substance on the floor behind the table.
Grissom processes the six Innoko water bottles on stage at the time of Dougie's death. Three were unopened, three were partially full. Brass tells him about Dougie's mantra. Grissom states that laughter is an involuntary motor response to survival issues: food, sex, body functions, and death. Brass replies "Yeah, it's a cruel world."
Catherine questions Alan about access to the Green Room and orders the comedians to give her their wallets. She gets around to the waitress, who has the same powdery white substance on one of her credit cards. She is arrested for possession and taken away. Outside, Brass spots someone familiar getting out of his red sports car with a blonde female going into a restaurant.
Medical Examiner Al Robbins confirms Dougie Max's cause of death: myocardial necrosis. No blockages were found and Dougie was positively healthy before his death. Grissom reported traces of cocaine found in his system, but Robbins reported normal nasal passages, clear lungs, and no track marks. Robbins told Grissom he has to process Dougie further.
Catherine interrogates the waitress with her attorney present. The waitress's attorney stated that she's willing to plead guilty to possession of cocaine and asks Catherine not to interpret her answers as criminal involvment. Catherine reminds them that is between the waitress and the District Attorney. She asked him about the cocaine found in his blood. The waitress told Catherine the cocaine is hers. She told Catherine about a "hum and coke" Dougie takes before performing. "Hum and coke" is essentially a sexual act involving the use of cocaine and a penis, which explains how the cocaine was absorbed through his penis foreskin and into his bloodstream. Catherine says when cocaine is snorted, it's a stimulant. Through the skin, it's a depressant. The waitress said that absorbing the cocaine through the skin to get a frustrated feeling, giving him the edge to perform well on stage. In a flashback, Dougie praised his sitcom deal for his new TV show, "Dougie to the Max!"
CSI Nick Stokes makes coffee in the break room when Brass approaches him about a few-weeks-old accidental death case in Green Valley. Brass did not call CSI on this case and ruled it himself. He recalls the victim's husband was very teary eyed when he found his wife dead in their bathtub. The night of Dougie Max's death, Brass saw the same man in the red Ferrari with the young girl going to a classy restaurant, raising Brass's suspicions about the husband. Brass called the husband's life insurance agent, who told him that the husband reported that his wife is dead on the morning of her death and demanded her money flatly without emotion. The insurance payout totaled to $750,000. Brass asked Nick to look into it instead of Grissom because Grissom is not interested in chasing down a hunch. He put together the original police report, autopsy protocol, detective summary, and the original scene photos for Nick to process.
Catherine argues with Grissom that no person can absorb enough cocaine through the skin to overdose. Grissom asks for her to cite a source and Catherine has no answers, reminding her to run the test scenario. Greg reports to them that Dougie's cocaine levels were 0.0497mg/liter, ruling out cocaine as the murder weapon. He also reported a secondary chemical was found: Naratriptamine, a new and powerful migraine medication. Dougie had 30mg /liter in his blood, 12 times the recommended dosage. Catherine and Greg respectively concluded that "Dougie was poisoned...to the Max."
Nick and CSI Sara Sidle reprocess the accidental death scene documents. They notice that the police did not use rulers or tag markers when photographing the scene. A towel bar was ripped from the wall. The autopsy was abbreviated since everyone investigating the victim's death (including M.E. Robbins) agreed that the death was accidental. Nick pointed out a contusion to the back of her skull was non-fatal. Cause of death reported was drowning. According to the files, the victim's name was Shelley Stark and her husband is George Stark. The detective's and George's accounts agreed that the death was accidental, but Nick pointed out that the notes, photos, and evidence from the scene was not taken and properly processed by anyone and a CSI was not present at the time. They both agree to process George's bathroom.
Grissom and Catherine begin processing Dougie's stomach contents, which many of the substances are a match to The Comedy Hole's consumables. Catherine remarks to Grissom that Spam cannot be absorbed through the penis and asked Grissom if he would like her to cite her source. Grissom says he would take her word for it. During their investigation, Catherine comes across a Choco-Bee and asks Grissom if it is "death by chocolate again?", referencing a previous case of the death of poker legend Doyle 'Candyman' Pfeiffer.
Nick questions George about Shelley's accidental drowning while sara paces around George's Ferrari. George is disturbed by Sara being too close to the car and asks her not to go closer to it or risk tripping its loud car alarm. Nick asks George for permission to reexamine his bathroom, but George is visibly nervous and does not wish to relive the painful experience of her death. Sara disturbs the convertible and the alarm goes off, drawing the neighborhood's attention. Reluctantly, George invites the CSIs in to process his bathroom.
The CSIs find that the bathroom was remodeled just days after Shelley's death. George explained that the bathroom only reminded him of his painful loss. When asked about the towel bar, George said a contractor threw it away and replaced the bathroom's fixtures. A real estate broker told him the house came in stock similar to many of the neighborhood's houses and advised him to invest in upgrades to sell. George is interested in leaving the big house and moving away. Nick thanks him and leaves with Sara dumbfounded by his decision.
Sara questions Nick's decision, which he defends because the original crime scene is gone, but they can recreate the scene using the scene documents and one of the neighborhood's model homes.
Greg presents Grissom with Innoko bottle #3 as the source of the poison. Grissom asks Greg to process the water for chemical impurities.
Nick and Sara use safety gear to recreate Shelley's accidental drowning. The accident report stated that Shelley has the same weight and size as Sara, making her the ideal test dummy. They think Shelley was slipping trying to get up from her bath and grabbed onto the towel bar. Sara was unable to pull the towel bar off the wall. Nick was able to rip it out easily because of his strength, indicating the accident was anything but.
Catherine and Grissom watch a female comedian butcher her act in an empty Comedy Club room. Alan flips on the red light, which is the equivalent to a stage hook used to pull acts off the stage if they are found to be not entertained. Barry tells the CSIs that tonight is Open Mic Night. Michael complains about the coffee the club brews and Barry brushes him off, charging him $5. When asked about Dougie's accomodations, Barry stated he was responsible for setting it all up. Dougie had high and lofty standards, demanding 6 pristine Innoko water bottles with their labels facing the Luxor and the Green Room all to himself with a silver tray holding Spam, blue Choco-Bees, and passion fruit. Barry is shocked to hear that the Innoko bottles have been tainted. Catherine brings up an old assault charge that Barry had. Barry explained that he beat up a heckler for interrupting his bit. He also admits to having headaches, possibly migraines. Grissom demands him to hand over Dougie's private stash of Innoko water.
While the police confiscate the Innoko water bottles and bring it back to the CSI lab, Grissom has Warrick process a dead body at a convenience store in Torrey Pines. Catherine checked Barry's medical records and counted 6 different prescriptions for migraines in 2 years. He is currently on Naratriptamine.
Warrick arrives at the convenience store and finds the dead body. He questions the store clerk about the kid who was scoping the shop. The kid stole a beverage, but put it back before the clerk could catch him. The clerk points out the place the kid was at last. To Warrick's surprise, he finds a bottle of Innoko water.
Catherine arrives and calls the Chief of Police about calling in a total recall of all Innoko water bottles in all Las Vegas businesses. Warrick asks an Innoko company representative to look into people who were fired from or had a grudge against Innoko. Greg arrives on the scene and takes the Innoko bottle from Catherine to process.
During an autopsy, Nick and Brass question Doc Robbins about Shelley's autopsy. According to Robbins, Homicide reported that no signs of foul play were found on the scene, hence Robbins' decision to perform an abbreviated autopsy on Shelley. When Brass and Nick ask him to sign off on a court-ordered exhumation, Robbins takes it offensively on many levels: his personal dedication to his work, the cost of the exhumation, and the reputation of the lab to the public eye. Nick protests Robbins' rationale, so Brass excuses Nick to speak with Robbins privately. Brass admits to Robbins that neither of the two want to admit having made poor decisions regarding Shelley's death, but asks Robbins to put personal reputation aside to find new evidence linking to Shelley's killer.
Greg processes the water bottle from the convenience store, which contains Naratriptamine as well. He reports this to Catherine. Catherine recalls that when Tylenol was first tampered with using cyanide, pharmaceutical companies began using safety seals.
Grissom searches for injection holes in the Speedy Mart bottle, but does not find any. Catherine spots powdery traces of Naratriptamine in the bottle caps.
David Phillips begins his first exhumation in his career, starting with Shelley Stark. Robbins and Nick walk him through the process. Shelley is well preserved due to her embalming, a process involving the removal of the decedent's blood, retarding bacterial growth.
News coverage reports that 15-year-old Casey Flynn was the victim at the Torrey Pines Speedy Mart, poisoned with the Innoko water. Lab technician Leah is disgusted about who would be capable of tampering with water and other people's lives. Lab technician David Hodges is more disgusted about having to process 40,000 bottles of Innoko water to find the people responsible. Greg recalls a cyanide case in an airport found easily by X-ray baggage scanners. Catherine briefs them about the tampering process. She believes that the killer dripped a solution of Naratriptamine into the threads of the water bottles. Capillary action pulled the solution into the threads, forming the white crystals they found.
Grissom examines the poisoned water bottles and figure out the two bottles have the exact same lot numbers. He asks Warrick for the confiscated bottles. Grissom matched the lot numbers to The Comedy Club, confirming the source of the poison. He believes the killer placed a bottle in a store away from the club to make it look like random product tampering to cover up one murder with another.
Robbins and Nick process Shelley's embalmed body. They notice some bruising on her back not reported in his abbreviated autopsy. Robbins uncovers more bruising on her face. The bruising shows a hand print on her face, turning Shelley's drowing accident into a murder.
Greg explains to Grissom and Catherine that the Naratriptamine was grounded up along with traces of caffeine. Catherine remembers seeing a coffee grinder in The Green Room at The Comedy Hole.
Grissom collects the coffee grinder from The Green Room. While there, Grissom asks Alan about his comedians' coffee habits. Alan responds that everyone gets generic brand at the club, making everyone bring their own brand if they wanted their kind of coffee. Grissom notices the wall graffiti with a sketch of Dougie Max and scathing comments about how he sold out on his craft.
Out in the front lobby, Grissom spots Dougie's memorial picture with the red light on. He asks why Alan switched the red light on, but Alan said he never touched the red light. Grissom asks for everyone's DNA samples.
Catherine begins swabbing The Comedy Hole's DNA. She spots Barry's hands, nails bitten off and bloodied. Barry admits to being a nail biter and switched on the red light during Dougie's bit.
Brass and Nick interrogate George Stark with his attorney present about his wife's accidental suicide. He remembered that George said "What am I gonna do? She was my life." Brass notes the past tense of "is", explaining that loved ones normally use the present tense when hearing the news of their loss. Whoever used the past tense are normally guilty, although it is not admissable evidence. Nick shows George and his attorney the postmortem bruising from her exhumed body. Since George is a murder suspect, Brass explains that no permission is required to exhume Shelley's body and reexamine her. He also notes that no defensive wounds were found because she loved him.
Crime Scene Reconstruction: Shelley was taking a bath when George walked into the bathroom. She told George how much she enjoyed her bath. George places his left hand on her face and uses his right hand to slam her head into the back of the tub. Shelley struggles to get free until she drowns. He broke the towel bar off the wall to make it look like an accident.
Despite this evidence, none of it can physically tie George to the murder. Instead, after George is free to walk away, a tow truck repossesses his Ferrari. Nick and Brass explain that although they do not have enough evidence to link George to Shelley's murder, they handed over their findings to George's insurance company to prove her death was not an accident. In this event, George's insurance company begins taking measures to reclaim Shelley's $750,000 life insurance payout beginning with George's personal assets. Nick also warns George this is simply the beginning of their murder investigation, which is still active.
Greg hands Grissom his chemical report. He explains to Grissom although they both enjoy Greg's Blue Hawaii brand of coffee because it is one of the finest brands money can buy, it comes nowhere as close to the brand found along with the grounded Naratriptamine---Kopi Luwak. Kopi Luwak's trace amino acid complex's chemical signature is formed from the excrement of a small Indonesian cat-like creature known as the Luwak. It is well known for its rich, chocolaty texture. Luwaks eat the ripest coffee beans, which pass through their digestive systems intact. In the digestive tract, enzymes break down amino acids, leaving its chemical signature. Greg deduces whoever drinks that brand of coffee is the killer.
Michael Borland is currently performing with another bad joke and steals Dougie Max's infamous mantra. He is seen drinking Kopi Luwak coffee onstage. Grissom is there to tell Alan to switch on the red light, signaling Michael to stop his bit. Before leaving the stage, Michael makes a mean-spirited and bitter, yet remorseful confession, claiming responsibility for Dougie Max's death and for Casey Flynn at the Torrey Pines convenience store. Michael also explains his motive for killing Dougie, despising everything he stood for---"dumb people" like the ones Dougie performs for. In his perspective, comedy is supposed to be about the truth. He is remorseful for killing Casey Flynn to cover up complicity in Dougie's murder. Michael blames Grissom for the whole thing, but he also says this was a joke. Grissom replies "I got it. It just wasn't funny." The police arrest Michael in the middle of the club for the two murders.