Nelson Lane finds himself once again assisting local law enforcement in Wyoming. This time, it's a tribal policeman enlisting the U.S. marshal's help to find a girl who has gone missing from the Wind River Reservation. It's a good excuse to take a break from playing messenger for banks foreclosing on errant ranchers, among other duties outside the scope of the job description. So, Nelson agrees, figuring the girl is just a runaway: An easy case to wrap up so he can get back to business at his favorite trout stream.
His search first leads him to a local moonshiner-found murdered at his ranch. Soon, Nelson suspects the killer must be one of the washed-up Chicago gangsters making their own moonshine in Wyoming, hoping to get back in the good graces of the bosses back home. At every turn, Nelson is thwarted by thugs out to kill him-including a crooked sheriff in the gangsters' pocket. When the marshal finally uncovers what they're really trafficking in, it may be too late to save the missing Wind River girl from certain death-if Nelson can even save himself.