At the hospital, a man pulling an oxygen tank staggers down the hall and goes into the office of a doctor. He beats the doctor, Whitcomb, to death with his oxygen tank, then hobbles back down the hallway.
Monk and Natalie arrive at the hospital after Adrian hits his nose with an ironing board. He's forced to wait for treatment and Natalie abandons him to go on a date. Monk eventually gets treatment but is nervous since a woman suggested someone she knew had a cerebral hemorrhage. The doctor tries cauterization but it doesn't work so Monk goes to see her superior while trying to keep his head back to staunch the blood flow. He arrives in Whitcomb's office and finds him dead, and bangs his leg on a table.
Stottlemeyer and Disher arrive to investigate and Randy bangs his shin on a low table. Drugs are missing but Monk quickly realizes that they were left to make it look like a junkie murdered Whitcomb. They find talcum powder and a tag for an oxygen tank with a room label for the Geriatric Ward. They go up and find themselves in the room of Hank Johansson. They match the tank to Hank's air tank but he says Dr. Scott was in charge of his treatment and he's been in the room the whole time. The nurse confirms that Hank was monitored the entire night, and sends them to Dr. Scott, who checked himself in to the nearby cardio ward. Scott says he thought he had a heart problem and checked himself in the previous day, and spent the night sleeping. Scott reassures Monk that his nose bleed is more psychological. As they leave, they notice talcum powder on his hands and a bruise on his leg. Disher checks and determines Scott's being sued for malpractice and Whitcomb was testifying against him. But Scott was hooked up to a heart monitor and has an iron-clad alibi.
The monitor tape confirms Scott was in his room and Stottlemeyer is frustrated, sending Monk home to rest. Natalie is going to dinner and while waiting for her meal starts feeling guilty. Monk is leaving but notices something on the roof and goes back to confront Scott on his rounds. Scott denies any involvement and Monk goes back to Hank's room where he notices a stain on the ceiling going into the next room. Monk investigates and finds a connecting door that's been covered over. He explains to Hank how Scott knew there were renovations and got himself assigned next door to Hank. Then he put his monitor on Hank's chest, took the oxygen tank, committed the murder, then returned to his room. Monk realizes that they can check the tapes and confirm the two cardiogram tapes will match. Hank congratulates Monk on his theory… but when the detective leaves, he calls Scott and tells him how Monk is nuts. Scott confronts Monk and knocks him unconscious with a crutch.
Natalie has dinner with her date, Alex, but notices a man and his medical assistant and her guilt proves too much. Meanwhile, Monk wakes up in a hospital bed unable to talk or move and Scott reveals that he's had Monk checked in under a false name as a patient who fell down a stairwell. Scott has ordered an injection of a drug that Monk is allergic to, killing the detective. Natalie arrives and visits Monk but he can't communicate his danger. The nurse arrives to administer the drug and Natalie leaves after trying to reassure him. As the drug drips into Monk's intravenous, the nurse mentions the false name Scott assigned to Monk. Realizing something is up, Natalie stops the drug flow just in time.
Later Monk is checking out of the hospital and despite several mishaps, decides he's better off not going back to the hospital for a long time to come.