9. Officer Blue

Complete story — includes the ending

After mounted patrolman Valasquez is shot down in the park, Mac goes looking for the bullet that killed the officer only to learn that it is lodged in his horse's spine and cannot be removed without being fatal to the horse (Officer Blue). The investigation leads the team to a local street vendor, but stalls when the D.A. asks Mac not to do anything to risk the horse until after the woman who donated it has a chance to say goodbye. Aiden investigates the body of a young man, Lenny Starks, who was found face-down, dead in the street. Aiden traces the young man to a local pizza parlor where she faces intimidation from the bookies who use it as a gambling front.