Scott Turner, an obsessively neat police investigator, acquires Hooch, a large and slobbery Dogue de Bordeaux, after the murder of Amos Reed, a local junk-yard owner who was a friend of Turner's. Turner is bored with little police work in the fictional town of Cypress Beach, California and is set to transfer to a better job in Sacramento while fellow investigator David Sutton is to be his replacement.
Turner pleads with police chief Howard Hyde to let him take on Amos' murder case. Believing that Hooch is the only "witness" he has, Turner brings him home. The energetic dog promptly destroys Turner's house, his car, and turns his life upside-down. On a positive note, however, Hooch also instigates a romance between Turner and the new town veterinarian Emily Carson.