A 12 episode serial starring Rex, the King of the Wild Horses and Rin-Tin-Tin, Jr. Rex is brought from the island of Sujan, where he is worshiped as a God-Horse, to the U.S. to be trained as a polo pony. He escapes, meets Rinty and with the help of Frank Bradley is returned to Sujan. The natives have been persuaded to turn against their God-Horse, however he is rescued just in time before he is burned as a sacrifice.
| Actor | Role |
|---|---|
 RexRex, The King of Wild Horses | Rex, The King of Wild Horses |
| RRin-Tin-Tin Jr.Rinty | Rinty |
 Kane RichmondFrank Bradley | Frank Bradley |
 Norma TaylorDorothy Bruce | Dorothy Bruce |
 Mischa AuerTanaga | Tanaga |
 Smiley BurnetteJensen | Jensen |
 Harry WoodsCrawford | Crawford |
 Pedro RegasPasha | Pasha |
 Hooper AtchleyDebor | Debor |
 Wheeler OakmanWheeler | Wheeler |
 Victor PotelKinso | Kinso |
| AAllan CavanMr. Bruce | Mr. Bruce |
 Al BridgeMitchell | Mitchell |
 Edmund CobbJones | Jones |
 Charles KingMartin | Martin |
 George ChesebroAnderson | Anderson |
 Jack RockwellMcDonald | McDonald |
 Ralph ByrdForest Ranger Jerry Morton | Forest Ranger Jerry Morton |