The Bandit of Hell's Bend, by Edgar Rice Burroughs. Part IV.

When Diana Henders' father dies and leaves her responsible for running a cattle ranch in Arizona, along with a gold mine on the property, she is left on her own to sort things out between two love interests, Hal Colby and Bull, both of whom are eligible foremen for the ranch. 

Then, trouble arrives in the form of her cousin Lillian and her lawyer, Corson, from New York. Lillian claims to own half the ranch, and wants to sell out to the Wainrights; a bullying father and son who own land nearby. Meanwhile, the shipments from the gold mine keep being robbed by the notorious "Black Coyote". 

The local sheriff seems completely unable, or unwilling, to put a stop to the robberies. Is Bull the Black Coyote? Is her half of the ranch worth fighting for? Diana needs to figure out who her true friends are, and whether or not her heart tells the truth.