Answer the following question: I am a movie director and I just received the following movie plot. Could you help me answer this question? If not, let me know by writing "Not answerable". Plot title: Electra Glide in Blue Movie plot: John Wintergreen (Robert Blake) is a motorcycle cop who patrols the rural Arizona highways with his partner Zipper (Billy "Green" Bush). Wintergreen is an experienced patrolman looking to be transferred to homicide. When he is informed by Crazy Willie (Elisha Cook, Jr.) of an apparent suicide via shotgun, Wintergreen believes the case is actually a murder. Detective Harve Poole (Mitchell Ryan) agrees it is a homicide, after a .22 bullet is found in the man's skull during the autopsy, as well hearing about a possible missing $5,000 from the man's home, and arranges for Wintergreen to be transferred to homicide to help with the case. Wintergreen gets his wish, but his joy is short-lived. He begins increasingly to identify with the hippies whom the other officers, including Detective Poole, are endlessly harassing. The final straw comes when Poole discovers that Wintergreen has been sleeping with his girlfriend Jolene (Jeannine Riley). The hostile workplace politics cause him to be quickly demoted back to traffic enforcement. Despite being demoted, Wintergreen is able to solve the murder. The killer turns out to be Willie, who confesses while Wintergreen goads him into talking about it. Wintergreen surmises Willie did it because he was jealous of the old man he killed, who frequently had young people over to his house to buy drugs. Shortly after, it is discovered that Zipper stole the $5,000, which he used to buy a fully dressed Electra Glide motorcycle. Wintergreen is forced to shoot Zipper after he becomes distressed and belligerent, and shoots an innocent bystander while brandishing a gun. As the film ends, Wintergreen is alone and back on his old beat, when he runs into a hippie that Zipper was needlessly harassing near the beginning of the film. Wintergreen lets him off with a warning but the hippie forgets his driver's license, and Wintergreen drives up behind his van to return it to him. The hippie's passenger points a shotgun out the back window and shoots Wintergreen, killing him. My question: Who is Zipper?
Answer:
John Wintergreen's partner.