Believe in Me by Sierra Cartwright

Protecting people, safeguarding secrets… For the men of Hawkeye, the line of duty between bodyguard and client isn’t meant to be crossed.
He was supposed to protect her, not risk both of their hearts.
Hawkeye Commander Garrett Young has an impossible assignment: protect heiress Charlotte Connelly—without letting the stunning beauty know he’s her bodyguard. Since she’s stubbornly refused protection, he can’t reveal why he’s romancing her on her secluded ranch hideaway.

After her fiancé’s crushing betrayal on the eve of their wedding, Charlotte is determined not to trust a man again. She’s definitely not interested in another relationship. But when she meets devastatingly handsome Garrett, his mysterious, powerfully alpha ways melt her resolve.

Charlotte soon finds herself opening the heart she swore was shattered, and she’s falling hard. Then Garrett’s dizzying web of lies crashes down, leaving her raw and hurt and unable to believe anything he says. But when her life is on the line, can Garett convince Charlotte that he truly loves her before it’s too late?