Who is Sergeant Pluck from The Third Policeman and what is their importance?

Sergeant Pluck is one of the policemen the narrator hopes will help him find the moneybox he's looking for. Pluck is the first policeman the narrator meets, and he assumes the narrator has a missing bicycle. Pluck himself, it turns out, steals bicycles and hides them, hoping to minimize the amount of time people spend on their bicycles. Pluck later arrests the narrator for murder, as a convenient scapegoat.