Testing the Limits (1998)

Mike and Toni are on their way to the mountains for a romantic weekend, when their car breaks down. The couple take shelter in an empty cabin, unaware that it is being used by bisexual photographer Jan who is on an erotic shoot with model Kristin. Things get more complicated when Glen, a fashion editor, arrives. Soon inhibitions (and underwear) are being freely cast aside. But the lovers' reverie is broken when Kristin's psychotic boyfriend breaks in, seeking vengeance.