European produced Western based on the novel by Friedrich Gerstäcker, set in the 19th century in a town on the banks of the Mississippi River. The area is plagued by a gang of pirates under the leadership of Captain Kelly, who live on an island in the river, from where they operate raids on passing steamboats and traders rafts, robbing them of their cargo and murdering the crews. Townspeople and settlers do their best to put an end to the crimes and rid themselves of the pirates and their daring leader.