Monk was originally a detective of the San Francisco Police Department. After the murder of his wife, a case which he could not solve, Monk became obsessive compulsive, refusing to leave his house for 3 years. Monk's personal nurse, Sharona Fleming, played by Bitty Schram, helped get Adrian back on his feet.
Eventually, Monk started his own private detective agency, helping the police solve difficult cases. Police captain Leland Stottlemeyer, played by Ted Levine, and and Lieutenant Randall Disher, played by Jason Gray-Stanford, are personal friends of Monk.