Nicholas "Nick" Slade is a former cop who left the SFPD to start his own private detective firm, Intertect. He hires Monk and Natalie to work for him when the SFPD fire him as a consultant. Ten years before the events of the book, Slade was given a tip by bar owner Bill Peschel that Linda Wurzel was looking for someone to kill her husband Steve. Instead of arresting her, Slade instead took the job and killed Steve. Ten years later, Peschel developed Alzheimers and believed he was still working at the bar and giving tips. If either Paul Braddock or Leland Stottlemeyer (who frequently visited Peschel) heard the tip that Slade had been told, they would realize he had killed Steve Wurzel. So he killed Peschel, making it look like an accident, then killed Braddock and framed Stottlemeyer. He tried to overwhelm Monk with cases so that he wouldn't have time for Braddock's murder, but Monk still figured it out. He followed Slade to the warehouse he met Linda Wurzel at, intending to kill her and eliminate the last person who might know what he did. Following a stand-off, Slade relinquishes, thinking that there's no proof that ties him to the murder. But Danielle Hossack and Natalie Teeger were secretly recording the interaction, implicating him and Linda.
Slade appears in Mr. Monk and the Dirty Cop.