Let's talk about sex, baby. No, really.

Since the season-long super-tease aired and revealed Kaitlyn Bristowe will sleep with one of her suitors, only to tearfully say she regretted it later, the question on every fan of The Bachelorette's mind has been, who does she sleep with?!

Now, just before the episode everyone's been waiting for is about to air, a source tells us that Kaitlyn sleeps with none other than Nick Viall, the runner-up of Andi Dorfman's season who returned in the middle of the season, in Monday's episode. (ABC had no comment.)

"It happened after they spent the day touring in Dublin. During the date, they had a hard time keeping their hands off each other," a source close to the show tells us. "When it was over, she invited him back up to her hotel room."