It's frontier vengeance times two─twice─in "Gunsmoke." After a rancher (Nick Stuart) is shot in the back by a scurrilous gunslinger (Craig Lawrence), the rancher's son (Stuart again) is wounded in a showdown with the killer. An injured Stuart is taken by a woman (Carol Foran) to an involuntary work camp run by an outlaw gang whose boss just happens to be the gunman's twin brother (Lawrence again)! Next, former Hopalong Cassidy sidekicks Jay Kirby and Andy Clyde set out on their own and team with Russell Wade to form the "Sundown Riders," a cowboy trio who tackle outlaws trying to swindle a gal out of her family's ranch. Marshall Reed, Jack Ingram lend support. 95 min. total. Standard; Soundtrack: English. Plays All Regions.