A Tender Masquerade — Linda Cajio

THEY WERE EQUALLY SKILLED IN THE ART OF DECEPTION
As war between Mexico and the U.S. looms on the horizon, Rafe Timmons, a man forced to forsake his heritage, works undercover for the American government. Assuming the identity of a dead businessman, Rafael Verdugo, he plays a dangerous game with one of San Diego's most ruthless rancheros in a power struggle Rafe is determined to win.

BUT PASSION WOULD UNMASK THEIR BOLD SECRETS...
But at Rancho Los Alisos, another deception has begun. Julietta Ruiz spends her days trying to protect her mother and younger sister from her tyrannical father's wrath. Under cover of night, she tends to the needs of the ranch's laborers, although it is forbidden to do so, and could place her in grave jeopardy.

...AND THEIR HEARTS
But soon, in the heat of desire, Julietta finds she cannot run from the yearning hunger the stranger called Rafael ignites. She gives herself to him, unaware of who he really is...or of a secret that could shatter her world -- and the truest love she has ever known....