Showing The Other Guy's Bride by Connie Brockway

Determined to prove her worth as a budding archeologist, Ginesse Braxton vows to solve one of the world's greatest mysteries--to find the location of the lost city of Zerzura. Unfortunately, no man dares take the risk of escorting the resolute young scholar across the open desert. But on her way to Egypt, Ginesse engages in a daring deception--she will switch places with Mildred Whimpelhall, who is traveling to meet her fiancé.

Cynical adventurer Jim Owen will do anything to escape the dark secrets of his troubled past. Betrayed by the woman he loved, scorned by proper society, he agrees to carry out a danger-fraught task: escort Mildred Whimpelhall across a lawless desert to her intended. But Jim is about to learn that "Mildred" isn't exactly what she seems . . . and the dangers they face together are eclipsed only by an even greater peril: falling in love, against all reason, with another guy's bride . . .