Feeling overworked, Natalie Teeger is delighted when her best friend Candace (no last name given) invites her on a comped trip to Kauai to be the maid of honor at her wedding. The only question is how to tell her boss, Adrian Monk, about the upcoming trip. She decides to drop the bomb at the last second: when Monk is on his usual high after solving a murder case – a well-known heart surgeon who was poisoned by his own patient while she was on the operating table – and tells him she's leaving the next day. He is devastated, and she quickly pushes him off to his normal appointment with Dr. Charles Kroger.
The next day, Natalie's peace of mind lasts all of one hour, when she wakes up midflight is shocked to see Monk sitting in the aisle across from her . Only now, he is "The Monk" – the infinitely-better-adjusted, but insufferably obnoxious persona brought on by Dioxnyl, a drug that relieves Monk of his fears and phobias but also limits his detective skills, and which Dr. Kroger assumed Monk had thrown out after the embarrassment he caused the SFPD the previous time that he tried it. Trapped, Natalie has no choice but to suck it up and accept him along, though she has a slight suspicion that Dr. Kroger put Monk on the drug so he himself could avoid being bothered over the week.
Upon landing in Lihue, Monk and Natalie meet Candace and her fiancé, Brian Galloway. Brian is full of adventure stores, many of which are repeated by his adoring betrothed. They also invite Monk to the wedding, saying the more the merrier.
Monk and Natalie check into the Grand Kiahuna Poipu resort in Poipu, Hawaii, which is playing host to a live taping by renowned TV psychic Dylan Swift. Natalie carefully arranges their room placement, anticipating the next morning, when the drugs will wear off. Monk is still drugged, but he believes that Swift is a hack after watching one of his shows.
The next morning, when the drugs do wear off, Monk is horror-struck at how he's spent the last twenty-four hours. But Natalie is firm about him behaving himself while they are on vacation.
At the wedding, Monk, to everyone's shock and embarrassment, speaks up and catches Brian in several lies – the whopper of which is, that he's already married to a woman in New Jersey, and was planning to travel back and forth between his two families. Furious and mortified, Candace slaps Brian and storms out of the wedding. As mad as she is at Monk for humiliating her friend, Natalie is also grateful that he saved her from a bigamist marriage.
With the wedding canceled, Monk is eager to go home, but Natalie counters that as their booking is for a week, and she plans to enjoy it. But as Monk and Natalie are walking, Monk spots a nearby crime scene. An elderly woman named Helen Gruber has been found dead in a hot tub after apparently being struck on the head by a coconut while bathing.
The local police lieutenant, Ben Kealoha, has ruled the scene an accident, but Monk announces that it was anything but that. Natalie is dismayed, realizing that this means her vacation is over. Inside the bungalow where the crime was committed, Monk notes some clues that prove the victim's death was not an accident: for one thing, he finds an impression on the ground indicating that the death coconut did not come from the tree shading the hot tub, but came from a tree a few feet away. Also, a slight bruise to the victim's collarbone suggests that she was actually killed in the kitchen and hit the counter as she fell. Many of the items placed nearby show that the scene was very hastily staged: the victim isn't wearing suntan lotion, also, there are no reading glasses despite the fact that a book found nearby is a large-print edition.
Monk and Natalie accompany Kealoha on a small trip out to a local cafe, where Monk is freaked out by the geckos on the walls and the bug zapper. Over lunch, Kealoha mentions that Helen Gruber came from Ohio, and that he plans on talking to her boy-toy husband Lance Vaughan. Monk, however, reaches the conclusion that Kealoha is suspecting him of being the killer based on where he's taken them. A call from Captain Stottlemeyer allows Kealoha to confirm who Monk really is, and any misunderstandings are cleared up.
Monk, Natalie, and Kealoha question Lance Vaughan, who seems like the obvious suspect in his elderly wife's death, but who admits that he was on a snorkeling trip at the approximate time that Helen died (pinpointed by the M.E. to be between 8:00 and 11:00 AM).
When Monk and Natalie do manage to get back to their rooms, Monk gets into a small argument with one of the hotel service employees about how his minibar is stocked. While doing so, he learns something interesting: Helen Gruber had been complaining to the front desk in the days prior to the murder about hearing voices out at the bungalow.
Natalie goes out to the beach for a swim. While at the beachside bar, she is approached by Dylan Swift. Using his standard medium pickup, he starts bringing up things about the murder, and claims to have a message from Natalie's late husband Mitch. He also has a message from Helen Gruber to Natalie, who in turn agrees to relay the message to Monk, although after the conversation is over, she suspects that Swift is merely an attention-seeking fraud seeking to get publicity from the murder case.
When Monk and Natalie are leaving on their way to the police station to meet Kealoha, they come across Lance in the process of moving rooms. Monk brings up what he learned from the hotel employee about Helen's "hearing voices", and Lance admits that he didn't bring that up earlier because it didn't seem right at the time. He also confides that the apparent dementia was part of the reason he went on the snorkeling trip that morning. As Monk and Natalie head for the rental office, they get another surprise: Brian Galloway, Candace's would-be husband, has had his car vandalized. He thinks it is one of Candace's friends who is involved.
Monk and Natalie rent a car from an airport rental dealership and go to the Lihue police station to watch the video from the snorkeling trip Lance was on, and they notice him ogling another woman. Monk also notices some information on a number of local burglaries, and notices that all of the burglaries happened at specific times of the day depending on the neighborhood, and asks Kealoha to join them for a game of golf at a local golf course the next morning.
Natalie reprimands Monk at dinner for offering to solve the mysterious break-ins, but Monk doesn't appear to mind. Noticing the mystery woman from the video, Natalie's curiosity is piqued, and under the pretense of taking an evening drive, she decides to see if Swift's messages are accurate, and they follow the mystery woman to another bungalow, where they find that this woman has been seeing Lance.
When Monk and Natalie return to their hotel room, Natalie decides to tell Monk about her meeting with Swift. She admits that she figured out the connection between Lance and the mystery woman based on what Swift told her. At this point, Monk decides to break down what Swift's routine is: he uses cold reading, where he tricks a person into giving him the information he needs to make it seem like he's getting his information from the afterlife. He makes basic deductions in order to make guesses about people, and also uses unique phrasing in order to reduce the amount of necessary wiggle room.This is just what Swift was doing on Natalie at the bar, although in general, his con works better when performed on a large group. Like the show they witnessed the day of their arrival: Swift had said he was sensing the letter "G" and a man named Gary got up and asked if the message was for him, and in turn, Swift then said that the message he was receiving came from a recently deceased member of his family, and said that her name had an "M" or an "E", or both letters in the same name, and he said the message was from his sister Margaret.
As for Natalie, Monk explains that what Swift did to her was use claims that he had messages from Mitch in order to win her sympathy and make her easier to prey on. Natalie breaks down crying as she recalls what Swift told her - he recognized the bikini she was wearing at the bar as one Mitch bought her, despite the fact that he never met the man once, meaning there should be no way Swift could know that Mitch had purchased said bikini for Natalie during a vacation in Mexico.
The next day, Monk, Natalie and Kealoha go to the local golf course, and Monk immediately exposes a mailman making deliveries to a nearby residential neighborhood as one of the burglars. While they are on the course, Kealoha mentions that Helen Gruber is Lance's third elderly wife. He marries elderly women and inherits their money when they die, and the last two died of natural causes.
Eventually, they catch a break on the Helen Gruber case - the mysterious woman who was with Lance Vaughan has been identified as Roxanne Shaw, also from Ohio. She and Lance are also known to be connected.
After Monk makes the cleaning crew fall several hours behind schedule by folding towels instead of rolling them, he and Natalie are moved to Helen's bungalow by hotel manager Martin Kamakele. When he is offering to move them, Monk and Natalie ask him questions about both Dylan Swift and Helen Gruber. Kamakele admits that Helen was referred to him by the front desk because she was driving customer service crazy with her claims about hearing voices. He also admits to being one of Swift's biggest backers, having a contract with him to film half of his shows in Hawaii (he films the other half back in San Francisco).
Monk and Natalie get a chance encounter with Swift while moving into the bungalow, as it turns out that he owns the one next door to theirs. Monk is naturally hostile to Swift and kicks him out when he starts making comments that are very invasive of Natalie's privacy and tries to fish for information on the killing.
In the bungalow, they find that some of the refrigerator shelves have been placed in backwards. Figuring that Helen's body was kept inside all night, Lance is arrested for the crime thanks to both the evidence and to Swift's information.
Having made the arrest, Monk and Natalie go out sightseeing. While they are stopping at a roadside curio shop, Natalie receives a call on her cell phone from Stottlemeyer, who mentions having heard about how Swift helped Monk in the newspapers. When Natalie mentions to Stottlemeyer the possibility that Swift is an attention-seeking fraud, Stottlemeyer notes that Monk is probably right. Since Natalie has previously told Monk to not try to nail Swift, she retracts what she said earlier and tells Monk to expose him by any means necessary.
As they are preparing to head back to Poipu Beach, they get hit by a pickup truck which then flees the scenes. Monk and Natalie are able to provide Kealoha a description of both the truck and the driver, who apparently ran a red light when he hit them. Curiously, Monk notes that the driver never even slowed down or even noticed that there was a red signal for him. They are driven back to the Grand Kiahuna Poipu resort. When they get back, Monk sees a front page news article about Swift's involvement. Enraged to have been used, he and Natalie confront Dylan Swift again. When they see him, he has a blister on one hand, which he claims he got when he burned his hand making breakfast that morning. They accuse him of using Helen Gruber's murder to boost publicity for himself. Monk brings himself to ask questions about Trudy's death, though whether he is just toying with Swift to draw him out or not is unclear.
That night, Monk and Natalie head to the hotel's luau. It starts off badly (thanks to Monk, of course), but things take a startling turn for the worst when the men digging up a roasted pig end up digging up a human body. To their shock, it's Martin Kamakele, the hotel manager, and it seems someone had beaten him to death with a shovel. Monk suspects that Kamakele's death has to be connected to Helen Gruber's death somehow, since the M.O.s are identical. But one detail tells him that Kamakele's death was probably an impulsive one: the roasted pig that the body was buried above was buried nine hours earlier, and the body was buried just over it, meaning that Kamakele was killed sometime that afternoon, and the killer was in such a rush to cover his tracks that the best he could do was delay the body's discovery. This suggests a crime committed in the heat of a fight.
Upon returning to the bungalow for the night, Monk tells Natalie a very moving Trudy story about her security blanket. The next day, Monk notarizes and addresses a letter to Stottlemeyer, and has it transmitted to the mainland.
Monk and Natalie receive a call from Kealoha, who has located their first car (the one that was stolen). They are driven out to a parking lot at a shopping mall in Lihue, and learn that the car was discovered when mall security prepared to have it cited and towed for being left unattended overnight. Monk notices the stains on the seats, and realizes that the car now has the car seats from Brian Galloway's car. He quickly rents another convertible that he has driven to the station.
Borrowing a knife, he cuts open the car seats despite Natalie's protests, revealing that they are packed with cocaine - Monk remembers Kealoha talking about how many goods have to be imported, and reasons that that fact of life also applies to drugs. Every fresh rental car is being used to smuggle in drugs, and the dealers are using inside men at the rental agencies to tip them off to which cars have the drugs. However, they can't steal the drugs by breaking into the cars while they're still in the rental lot, because the lots are under 24 hour surveillance. Instead, they get the cars into the body shop where the drugs are removed by sending men out to wreck, vandalize, or steal the rental vehicles, knowing that seemingly random thefts and accidents involving rental vehicles are not likely to be something the police or rental agencies will be suspicious of. Once in the shop, they switch out the drug loaded seats for emptied seats from the last drug-transporting vehicle. Kealoha acknowledges that there is one body shop in the town of Kapaa that gets most of the body shop work for auto repair work, and concludes that said body shop is probably a front for illegal activities.
The next day, Monk takes his Dioxynl for their flight back to San Francisco. The day after they get back, Natalie gets a rather sudden wake-up call from Monk, who wants to expose Swift as the fraud he is. Monk and Natalie go downtown to the set prior to another taping, and find Stottlemeyer and Disher waiting for them, Stottlemeyer holding Monk's letter.
Swift spots Monk and invites him up, claiming to be receiving a message from Trudy on the other side. He somehow reveals his knowledge of the security blanket that Monk mentioned to Natalie, and this is when Monk decides to tell all and expose Swift as not just a fraud, but also a double-murderer. He has Stottlemeyer read his letter, in which Monk admits that he told only one person (Natalie) the story about Trudy and her security-blanket, and appears to have predicted that Swift will tell this story to them. The shocker is the point in the letter where Monk admits that the story that Swift has just brought up is a complete fabrication. He concocted the whole thing to prove that Swift isn't just a fraud, but also a double murderer. As it turns out, Swift's way of obtaining information from his unsuspecting audiences isn't just by cold-reading, but through the fact that he's bugged all of the hotel rooms at the hotels where he does his tapings.
Here's What Happened
Helen Gruber happened to use hearing aids, and when she moved into the bungalow next to Swift's, she complained to the front desk that she was hearing voices - she was actually hearing transmissions from listening devices placed in the bungalow. Swift had to kill her so that she wouldn't figure out what she was really hearing. Monk became an unwitting accomplice to Swift's plan: when Swift saw him at the hotel, he saw an opportunity to capitalize on the murder by helping Monk solve the case. However, he now needed to find someone he could frame for the murder. Thanks to the bugs, Swift had hours of recordings through which he knew all about Lance, his relationship with Roxanne, and Helen.
On the morning of the murder, after Lance and Roxanne left, Swift broke into the bungalow, struck Helen over the head with a coconut, and then put the body in the refrigerator for long enough to leave forensic clues that would suggest that she had been kept inside during the night. Then Swift planted the body in the hot tub and carefully staged a crime scene that he knew Monk would recognize as fake.
While Swift thought his plan was foolproof, one person quickly figured out what he'd done: Kamakele, his backer who had wired the hotel rooms on his behalf. He figured out Swift's involvement after news broke about the closure of the case, and confronted him. In the resulting argument, Swift beat Kamakele to death and then buried his body in the roasting pit, burning his hand in the process, creating the healing blister on his hand.
Swift says that there is no proof, but Monk reveals that since he can't speak to the dead, the only way Swift could have known all of the things he said in Hawaii is if he was the killer. Swift is subsequently arrested.
As Monk and Natalie walk back to their car, Monk reveals that his moving story about Trudy's security blanket had to sound convincing so that Swift would take it a fact. In fact, it is in every way true, except for the fact that said security blanket was actually his mother's.