Mr. Monk and the Dirty Cop
Lee Goldberg Audio Book

Captain Leland Stottlemayer is faced with budget cuts and trims Monk's services as an expense. Though he insists it's nothing personal, when Monk's offers to help for no charge are declined, he and Natalie suspect otherwise. But Monk is too compulsive to stop investigating. So when Stottlemayer is arrested for the killing of another cop with overwhelming evidence against him, he must turn to the only detective who can prove his innocence.