Three Musketeers of the Mesas in a rough riding romance of the roaring West! William Boyd plays the title role for the first time in this, the first of 66 Hopalong Cassidy features. In this one, Cassidy helps warring cattlemen join forces to battle a gang of rustlers. George Gabby Hayes and James Ellison also star, but look for Charles Middleton, best known for playing Ming The Merciless in the old Flash Gordon serials, as ranch foreman Buck Peters (a role originally offered to Boyd).