Ryan Sharkey Jr. was a police sergeant for the San Francisco Police Department in Mr. Monk and the Captain's Marriage.
Originally a motor officer, Sharkey was a recent transfer from Mendocino. While he was highly decorated in his career and the recipient of two medals, in secret, he was a corrupt cop and on the payroll of crime boss Michael Karpov. Under Karpov's orders, Sharkey lured Jimmy "Chicklet" Botsdale, a small-time dealer and suspected informant, to a junkyard and confronted him with the accusations before attacking him with a taser to prevent him from speaking out against Karpov, eventually beating him to death. However, one of Sharkey's teeth was knocked out during the fight, and because Gerald Vengal, a homeless man who witnessed the altercation, had just signaled a nearby police officer, he didn't have time to get rid of his DNA. When back up arrived, he overheard Leland Stottlemeyer arguing with his wife Karen over the phone. Realizing Stottlemeyer was having trouble in his marriage, Sharkey figured he could provoke Stottlemeyer into hitting him if he acted like he had a sexual encounter with his wife and then pretend his tooth was knocked out because of it. He would further expand on this by claiming that he was having a full-blown affair with Karen to aggravate the captain even more, both for his cover story and to spite Stottlemeyer for his own amusement. He also attempted to kill Vengal, who could identify him, by throwing him out of a building, but Vengal survived.
Sharkey was exposed by Adrian Monk when the latter saw him eating an apple with the left side of his mouth, but Stottlemeyer, a right-hander, would have knocked a tooth out on that side, not the right, where his tooth is missing. That, plus the fact that Sharkey was recently transferred from Karpov's hometown of Mendocino, and the fact that Karpov referred to him as a sergeant during a lineup, despite being plainclothed, makes Monk realize that Sharkey is working for Karpov. This is further cemented when Vengal positively identifies him as Botsdale's killer. Sharkey is arrested on counts of homicide, police corruption and attempted murder.
Sharkey's lies did, however, have an effect even after they were disseminated, as it showcased the friction and distrust between Leland and Karen, which prompted the latter to reveal that she had been seeing a divorce lawyer behind his back and would be kicking him out of the house after it was finalized.