Koko

Rex Allen ('Rex Allen'), a U. S. government veterinarian, rides into the picturesque town of Pine Rock, near the Canadian border, to take the place of the regular vet who is on vacation. Used to doctoring animals in Texas, Allen finds out that herein the heart of the fox-farming industry, he is to doctor the most finicky and high-priced of fur on four feet. On the farm of Mel Richards (Tom London), Allen learns the habits of the valuable creatures from Richard's niece, Jane (Mary Ellen Kay, and her ten-year-old brother Danny (Jimmy Moss'), and on his own learns that the trusted owner of the trading post, Steve Baxter (Roy Barcroft) heads a gang that is smuggling counterfeit money across the American/Canadian border in the fox cages.

Anchor is building a railroad and to get cheap labor he gets Black Hawk's Indians to attack and burn the incoming wagon train. This forces the settlers to work for Anchor and he pays them in devalued scrip. When Rex figures out Anchor's swindle, Anchor gets Black Hawk to capture him. When Anchor turns on Black Hawk and shoots him, Black Hawk gets a chance to repay a debt to Rex.

One-time cavalry officer Rex Allen, between jobs as a star rodeo rider, is asked by his former commanding officer, Colonel Bigelow, to help settle a dispute between the army and local ranchers. The cavalry has commandeered a large parcel of land needed to test their newly-designed tank and prominent rancher Jenson has encited the locals to rebel at this intrusion. It is up to Rex and his sidekick, Slim, to thwart Jenson and convince the residents that these army tests are essential.

Ex-cavalry buddies, Rex and Slim, band together to capture a wild stallion, solve a murder and thwart the killers from cheating a boy out of his inheritance.

The Hurley's own a lumber mill and want to harvest all the timber in the valley. They kill the Forester and substitute their brother Dusty in his place. Dusty then says all the trees are infected and must be cut down. But Rex Allen is suspicious and writes to the Forestry Department and gets involved with the murders.

Rex Allen against diamond smugglers down Laredo way

Lacey is after the profits of the Foster and Morales rodeo show. He has Morales killed during a stunt and then forces Foster to take him on as a silent partner. When Rex Allen joins the show, Lacey tries to get rid of him also. But Rex survives and now believes Morales' accident may have been murder.

Two men searching for black pearls are marooned on an island when their crew mutinies. There they run into a beautiful girl who had been washed up on the island in her childhood. They must fight angry natives and a typhoon in order to survive.