In His Collar (Restrained #4)
Patricia D. Eddy

When his sponsor begs him to investigate a local BDSM club, Nicholas can’t refuse, but the painful errand yields one interesting encounter—lovely bartender Sofia.
Sofia doesn’t have time for dating—let alone a relationship with disgraced former billionaire Nicholas Fairhaven. But something about Nick’s disarming smile and self-deprecating humor calls to her, and she finds herself in his bed.
How far will Nick fall? And will he drag Sofia down with him?