Ever since Robby's father was killed while on police duty, Robby has been angry and alone. His father's old partner, a police dog named Marlowe, suffers the same fate. So when Robby sees Marlowe alone and locked up in a cage he begs his mum to let him have him. Instantly, the two are best friends. But, being a cop dog, when Marlowe, sees two familiar criminals in the woods (the same two crooks Robby's father was investigating when he died) Marlowe immediately chases them, right into a busy street. By the time Robby and his best friend Deb catch up, it's too late. Marlowe has been hit by a speeding car. Devastated, Robby slips back into a reclusive state. But later that night, Robby hears barking outside. When he goes to investigate, he sees Marlowe. Soon, Robby learns Marlowe has come back as a ghost. The Cop Dog has unfinished business to take care of. His new mission is to help Robby find the two crooks and solve the mystery of the death of Robby's father.