Just 45 minutes away from his scheduled execution, death row inmate Ray Kaspo dies in his cell from a poisoned last meal. Monk is brought in to investigate, but turns down the case - until he receives a call from his old nemesis, Dale "The Whale" Biederbeck, who is locked up in the same prison as the murdered Kaspo. It seems that Dale is a prime suspect in the murder, and he needs Monk to find the real killer in order to get the authorities off his back. In exchange for Monk's help, Dale promises to provide information relating to the death of Monk's wife, Trudy.
Monk agrees to take the case, and immediately hones in on the cook who prepared the victim's last meal. The cook is found dead with money stuffed in his pocket, explaining how the meal was poisoned, but not who was ultimately behind it. Then Monk gets a lead from prison social worker Sylvia Fairbourn, who thinks another inmate, the dangerous Spyder Rudner, might be the culprit. Monk arranges to go undercover and share a cell with Spyder, who surprisingly takes a liking to Monk.
Spyder turns out to have had nothing to do with the victim's murder, and Monk realizes that Sylvia Fairbourn must have been setting him up. Now Monk turns his attention to Mrs. Fairbourn, deducing that it was she who arranged to kill Ray Kaspo. Her motivation? Mrs. Fairbourn's son had written a best-selling unauthorized biography of a reclusive millionaire, Lambert Lawson, who in turn sued her son for libel. With her son standing to lose millions of dollars to Lawson, Mrs. Fairbourn devised a sneaky way to kill the millionaire: Lawson was awaiting a kidney transplant from none other than Ray Kaspo, so Mrs. Fairbourn arranged to have Kaspo killed with enough poison to eat away his internal organs, thus spoiling Lawson's transplant and also ending the millionaire's life.
Knowing that Monk is on to her, Mrs. Fairbourn arranges to have Monk killed by a ruthless gang of prison Nazis. Surrounded by a crew of Aryan assassins, Monk is rescued from certain death by his new friend, Spyder Rudner. The authorities clamp down on Mrs. Fairbourn, and with Monk having held up his end of the bargain, Dale "The Whale" gives Monk the information he promised regarding Trudy's death: 1) the car bomb that killed Trudy was intended for Trudy, not Monk; and 2) a man connected to the murder named Warrick Tennyson can be found in New York City.
With this information in hand, Monk begins to make plans for a trip to New York, and he learns that the whole crew - Sharona, Captain Stottlemeyer, and Lieutenant Disher - will be going with him...