After Alex confesses to Allie that he wants both her and his best friend Charlie in his bed, Allie skips town like a thief in the night. Now, six years later, Allie is back in their lives, all grown up and more alluring than ever. What starts as a night of three friends catching up turns into intimate explorations in Charlie’s truck…and Alex’s shower…and his king-size bed…

While Alex and Allie are thrilled with the threesome, Charlie struggles with the idea of sharing Allie and with his newfound feelings for his best friend. A hot encounter at the office—with Alex bent over his desk—only confuses Charlie further. It’s up to Alex and Allie to convince him that two plus one can equal love.