Her most challenging task?

Seducing her partner.  

After infiltrating a powerful Colorado crime family, FBI agent Angie D'Angelo gets a startling assignment: pretend to be lovers with Julian Parisi. But how, she wonders, will working with the attractive mobster help shut down a human trafficking ring and find the missing women? When pretense becomes a hot reality, Angie discovers that Julian has a mind-blowing secret that could jeopardize her undercover mission—and their lives.   

From Harlequin Intrigue: Seek thrills. Solve crimes. Justice served.