The Man From Stone Creek — Linda Lael Miller

There was trouble in Haven, Arizona, and Ranger Sam O'Ballivan was determined to sort it out. Badge and gun hidden, he arrived posing as the new schoolteacher, and discovered his first task was to bring the rough ranchers' children under control. So he started with a call on Maddie Chancelor, the local postmistress, and older sister of a young boy in firm need of discipline.

It never occurred to Sam that Maddie would turn out to be a graceful woman whose prim and proper stance battled with the fire in her eyes. Working undercover to capture rustlers and train robbers was a job that had always kept him isolated and his heart firmly in check--until now. But there was something about the postmistress that had him unwittingly tempted to start down a path he'd sworn he'd never travel.