When Rosewood and Villa suspect a brilliant doctor has killed two of his patients, they must find a way to make their case with limited evidence. Meanwhile, Villa spars with Captain Hornstock when he discourages her from pursuing an uncertain case. Also, Rosewood receives an anonymous letter revealing something that could change his life forever.

When Captain Hornstock becomes the prime suspect in his third ex-wife's murder, he turns to the only two people he can trust to prove his innocence, Rosewood and Villa, forcing them to repair their severely damaged relationship in hopes of clearing his name. Meanwhile, Shirley's revelations lead to emotional consequences for Rosewood and Pippy.