While the original title, "Trailing the Killer" isn't a misnomer, it was a bit misleading since the "trailer" is a dog named Caesar (Caesar the Dog) and the killer is a mountain lion. But the makers also pointed out that Caesar "is the most intelligent dog actor since Rin-Tin-Tin" which probably lured a few Rin-Tin-Tin fans with a show-me attitude. Caesar prowls around the woods of the Northwest, dispatches a rattlesnake, visits his she-wolf mate and their pups, pauses to watch the dainty habits of a raccoon personally washing every morsel of food before eating it---and that raccoon had enough food to use up several minutes of running time---and then saves sheepherder Pierre (Francis McDonald)) from getting eaten by one mean mountain lion. Rin-Tin-Tin he ain't, but then who was?

Cowboy is hired by an archaeologist to help find "Hidden Valley", where an Indian gold treasure is supposed to be buried. Just when he finds it, the archaeologist is killed, and the cowboy his charged with his murder.

Doctor Smith and his wife, Mary,depart a riverboat and are met by Phil Talbot. Phil informs Dr. Smith that Jessup, the only other white man in the village, has died while the doctor and his wife were off on a two-day holiday. Unknown to Smith, Jessup and his partner, Ross King, had a large cache of ivory tusks in the jungle, and he had told Phil about it. Meanwhile, Mary Smith has decided to steam-boat down the Congo River to Capetown for an extended holiday. Kuba, King's gun-bearer, asks Smith to write a letter to King, currently residing at a New York City Explorer's Club, and advise him that his partner has died. Talbot sends a letter to his stateside sweetheart, Diane Cameron, and her father, asking them to come to Africa and join him on an ivory-treasure expedition, and replenish their family-fortune lost in the recent stock-market crash. What Mr. Cameron and Diane don't know about Talbot is that his years in Africa have unhinged him...