A rather mundane effort for the usually fast-paced Mascot Pictures, this 12-chapter action serial featured Rex, billed as a "Wild Stallion," and the redoubtable Rin Tin Tin Jr.. Rinty's offspring was not in his famous father's league and his teaming here with Rex and Bob Custer, a wooden and increasingly stout silent Western star, did not earn him many new admirers. The two animal stars are pals attempting to save their owner, Bob Sheldon (Custer), from a murder rap. Falsely accused of killing Lou Salter (Dick Alexander), rancher Sheldon is arrested by the sheriff (Jack Rockwell). His accuser, Frank Nolan (Richard Cramer), then steals the condemned man's handsome stallion, Rex, whom he expects to ride in the Big Race. With the help of Rinty, lovely Alice Ingram (Lucile Browne) and her sidekick, Henry (Ben Turpin), manage to locate Rex in a barn. In order to raise money for Sheldon's defense, Alice enters the race on Rex and wins. Rinty and Custer both fell on hard times following The Law of the Wild but were briefly resurrected by Poverty Row company Reliable for a rather shoddy B-Western effort entitled The Vengeance of Rannah (1936).