A visitor to a big city gets involved in intrigue when a look-alike jewel thief sets out to doublecross his gang.

A prospector is murdered by The Cactus Kid and his gang, who hope to find the murdered man's goldmine. The miner's dog, Rin-Tin-Tin, recognizes the killers, who thereafter seek to use the dog to locate the lost mine. With the help of a government agent and a young girl, Rinty saves the mine and brings the bad guys to justice.

Two competing jewel thieves hunt for a load of diamonds.