Lawman in Disguise (Brides of Simpson Creek)

The Lawman's Secret 

When her son discovers an injured outlaw in their barn, the mysterious stranger instantly turns widow Daisy Henderson's world upside down. But Daisy senses Thorn Dawson's a good man…and there's more to his story than he can tell her. So she can't turn him away before he heals, even if she's falling for him—something she swore she'd never do again after her husband died. 

An undercover lawman, Thorn never lets himself get too close to anyone. But that's before he meets single mother Daisy and her spirited son. Now Thorn has to protect them from the Griggs gang—a gang that's come to accept him as one of their own. And if he can't keep up the charade, the woman of his dreams might just pay the price.