Out of the Dark — Megan Hart

On the night of her cousin's bachelorette party, Celia Henry meets the man of her dreams. Geologist Luke Gaines is smart, handsome--and pleasures her in ways she's only dreamed about. He's the perfect antidote to her sexual dry spell, even if they only have a one-night stand.

Six months later, however, Luke returns--changed. He's survived a cave exploration gone horribly wrong...and learned the truth about the creatures hiding in the darkness. Now he hunts the monsters that torment him, finding solace only in Celia's bed and the explosive passion they still share. But will their love be enough to make Luke stay with Celia, or will his mission draw him away for good?