Chase Hawken's quest for vengeance is almost complete. Two years before, his young wife was brutally raped and murdered by the Lawton gang, but Chase wasn't about to let those men get away with cold-blooded murder. He was legendary as a cavalry scout years before and used those skills to track down each and every member of that gang to make them pay. Now, only two members of that gang remain alive.
Indigo Moon begins in Washington Territory where Chase has tracked down one of the two remaining gang members, Mike Lyon, aka Lyons, along with a young man, Nathan Randall, and takes them to jail for bank robbery. Both men are scheduled to hang the next morning and once Chase sees Lyons dead for himself, he will continue his pursuit of the last gang member, Cherokee Johns.
At least, that's the plan until a widow pleads with him for his assistance to lead her and her group through a treacherous mountain pass in the middle of a snowstorm. However, this is no ordinary widow. In fact she isn't a widow at all. The woman is Rebekah Randall, Nathan's sister who has come to break him out of jail.
The trouble starts when Chase realizes she looks exactly like his wife who's been dead the last two years, and she's enlisted the help of Cherokee Johns to break her brother and Lyons out of jail. Chase grudgingly allows himself to be "persuaded" into helping them with their plan of escape, while he secretly plots a way to help Rebekah and himself get away from this murderous band.
Important secondary characters include the sheriff who was going to oversee the hanging, and is Chase's best friend and was his wife's brother, as well as Jim Braggard, the local army commander who shares a history with Chase and has secretly loved Rebekah for years. In fact, most of the characters are so deeply interwoven with one another that it's difficult to decide who's a main character and who's a secondary character. All of the characters are important to the balance of the story.
While the overall plot of the book was drawn out and occasionally implausible, the interesting storyline was its redemption. Indigo Moon is the story of a man given a second chance at love, and a woman who will do anything to protect the people she loves and who accept her for who she is.