Promising Hearts is the sequel to an earlier Radclyffe novel Innocent Hearts. It brings back the characters of Jessie and Kate, partners who are running a ranch in Montana, Mae, the kind-hearted madam of the local saloon, and introduces Dr. Vance Phelps, a one armed female Civil War veteran.

Vance arrives in the Montana Territory under less than positive circumstances. In the last skirmish before Lee surrendered at Appomattox, she was wounded badly enough that she lost her left arm from the elbow down. She had faced a difficult enough future as a female surgeon in the 1860's. To be a one-armed female surgeon seems impossible, so she has arrived in the West with her confidence shaken and her career appearing to be at a dead end. Instead, Vance finds a kindred spirit in Jessie, a friend in Kate, and Mae, a woman who accepts Vance exactly like she is and only wants to help her heal. This quartet has a lot to deal with. It would seem to be enough that they are lesbians leading an unconventional lifestyle in a small town on the frontier in the 19th century, but they also have to contend with cowboys, rustlers and the town's society ladies. They draw on each other's strengths to survive and carve out a place for each of them in the community while discovering the ability to love deeply..