The Hero Within by Bec McMaster

As the only healer in a war-stained town, Eden McClain is devastated when the Salt Plague sweeps through the wastelands she calls home. Suddenly she’s racing against time to save her people–and her niece–before it’s too late. When she hears whispers of a cure, she knows she can’t cross the dangerous Wastelands by herself to get it. She needs a guide. And she’s just desperate enough to turn to a man who once betrayed her.

Redemption comes at a price…

After years of living on the leash of a dangerous psychopath, Johnny Colton is finally free, but that doesn’t mean he can wash the blood off his hands. The easiest way to deal with the past? Just stop caring. Which is working perfectly for the rugged outlaw, until a beautiful ghost from the past rigs a trap for him.

The last person he wants to see is the woman who haunts his dreams, but as Eden points out, he owes her one. The only problem is that the people with the cure might also have created the plague, and deliberately unleashed it. It’s a dangerous trap, and the only way to escape it is for two past enemies to learn to trust each other