Mr. Monk is a Mess is the fourteenth novel in the Monk mystery book series by Lee Goldberg, published on June 5, 2012.
After arriving home in San Francisco after working as police officers in Summit, New Jersey, Natalie Teeger finds a dead body laying in her bathtub. During the investigation by the police, marked money from a federal sting operation is found stuffed under Natalie’s mattress. Natalie now needs Monk's help, but Monk is preoccupied with his own investigation. He's helping his brother find his missing girlfriend Yuki Nakamura, which is a problem that Monk is conflicted about, since he's happy to see Yuki leave.
As the case continues, it becomes clear that Yuki has a dangerous past, and that they are chasing a ruthless, cold-blooded killer.