The dramatic thriller In the Cut (opening Friday) features stars Meg Ryan and Mark Ruffalo in very spicy sex scenes. So explicit, in fact, that director Jane Campion was obliged to make a tamer U.S. edit to avoid an NC-17 rating. When reporters asked Ryan how she approached the challenge of shooting such risqu&#233 footage, she mumbled something about discussing sex "globally, thematically and intellectually." Huh? Luckily, Ruffalo had a better way to describe their awkward task.

"You know what we're going to do today?" he quipped. "We're all going to take our clothes off, to feel what it's like."

Alrighty then! "To deal with these things, [you have to] establish boundaries," added the actor, who's best known for his breakout role in 2000's You Can Count on Me. "I'm happily married. You establish that you're not there to mess around. It's a professional environment. I've been doing it for so long, and I had a hundred affairs in acting classes with every actress I did a love scene with. It was a nightmare."

In Cut, Ruffalo plays a homicide detective who's investigating a murder that occurred near the Manhattan apartment of Ryan's character. As he questions her, things take a decidedly unprofessional turn. Ruffalo says affairs like this aren't just the stuff of naughty imaginations, as he discovered after speaking to several cops. "This happens," he said. "I don't know what the whole story is, because I never talked to the women, but it's a very flirtatious thing. They'll canvas a building [for witnesses], and there's a type of woman that really likes cops, so it happens... That's a whole 'nother culture."