John Wintergreen (Robert Blake) – a 5 feet tall motorcycle patrol officer somewhere in the vicinity of Monument Valley in Arizona – begins the day pestering his captain for a transfer to homicide. His imbecile partner Zipper (Billy “Green” Bush) feels they have a good life riding motorcycles for a living, but Wintergreen dreams of “that brown suit, that Stetson hat and four wheels under me instead of two.” Zipper harasses a hippie they pull over, but Wintergreen is fair-minded and honestly wants to help people.
He gets his chance when the patrolmen come across a desert rat (Elisha Cook Jr.) babbling about his best friend killing himself. Responding to the scene of the crime, Wintergreen finds it odd that the deceased supposedly shot himself in the chest. A coroner (Royal Dano) doesn’t want to hear Wintergreen’s amateur theories, but homicide detective Harve Poole (Mitchell Ryan) commends the officer. “Incompetence is the worst form of corruption. Glad there’s someone around here who understands that.”
Poole recruits Wintergreen to serve as his driver. The patrolman is so by-the-book that while searching a commune for their suspect, Wintergreen politely accepts everyone’s word that they don’t know anything. Poole is eager to transform his diminutive protégé into the best damn detective in Arizona, but when he discovers the local bartender (Jeannine Riley) he’s smitten with has slept with Wintergreen, their working relationship goes south. Meanwhile, Wintergreen develops his own idea of who their killer is.