While on spring break vacation in Mexico, Chip Rosatti, the son of a prominent San Francisco businessman (a businessman who also happens to be a close friend of the mayor), wins a free skydiving jump. Watching from the ground, two of his friends gaze up in horror as Chip leaps from the plane but fails to open his chute and plummets to his death. When Chip's body is examined at the morgue, local coroner Dr. Madero discovers some perplexing news: Chip Rosatti didn't die from hitting the ground - rather, he drowned in mid-air. A call from the Mayor of San Francisco sends Monk to the Mexican vacation spot in order to figure out just what happened during that fall.
Prepared with 18 suitcases filled with everything from backup pillowcases to pre-packaged food and water, Monk and Sharona arrive in San Marcos, Mexico, and are greeted by Hispanic counterparts of Captain Stottlemeyer and Lieutenant Disher. The Mexican police insist Chip's death was drug related, but Monk isn't convinced.
After a visit to the medical examiner's office, Monk questions the two friends who watched Chip's jump, and both swear he was alive when he leapt from the plane. Monk listens to their story, but has trouble concentrating on their testimony: just moments after his arrival, all of his suitcases were stolen from in front of the hotel - and along with them, Monk's entire food and water supply. A creature of habit, he can't bring himself to drink any other brand of bottled water than the one he had brought with him, and as a result, he begins to suffer from dehydration. To further complicate matters, he is nearly run down by a speeding truck in an alleyway.
Monk and Sharona talk next with the pilot of Chip Rossati's plane. He also claims Chip was alive when he jumped, and further explains that the free jump certificate that Chip won turned out to be a forgery. In addition, he reveals that Chip's parachute had been tampered with, and that it could have easily been accessed by anyone.
Digging deeper, Monk discovers a key to a bus station locker that Chip was renting. As he makes his way to the bus station, he is once again nearly run down by a mysterious driver. Clearly, someone doesn't want Monk in Mexico. And just who that someone is soon becomes crystal clear to Monk when the Mexican police tell him about a similarly bizarre murder just a few years ago in which a man was mauled to death by a wild tiger. A wild tiger? In Mexico? Now Monk has all the clues he needs to point a finger - at the seemingly innocent coroner, Dr. Madero.
Monk concludes that it wasn't a drowning that kept Chip from pulling the ripcord on his parachute: Chip didn't pull the cord because the chute had been tampered with and the cord had been cut. Chip also didn't "drown" until after his body arrived in Dr. Madero's office: that's when the coroner filled the dead boy's lungs with water to make it appear that it was an inexplicable death.
But why? As it turns out, Madero's medical career in the United States was derailed couple of years earlier when Monk testified against him. Wanting to get revenge but unable to return to the US, Madero cooked up a plan to get Monk to come to Mexico in order to kill him. And what better bait than the seemingly impossible death of a San Francisco teen with ties to the mayor? An almost perfect plan... if not for the deductive prowess of Adrian Monk.