On Valentine's Day, I personally tied my fiancé and my best friend to a hotel bed.   Julian Prescott took three cold showers, then came out of the bathroom and frowned at me.   "Can you stop acting insane? Do you really want me to sleep with someone else that badly?"   I stood beside the camera on its tripod, frozen.   Ever since I received a photograph of him passionately kissing another woman on the street, I had suspected every woman who lingered around him.   Each time I booked a hotel room and arranged another test, Julian would laugh, push me out, and later throw the recording at me.   "You arranged it. I might as well enjoy myself."   Over two years, we played that game 30 times.   I thought we would keep tormenting each other until we were old.   But this time, he was furious.   He pulled a blanket around Lydia Sutton and stared at me with bloodshot eyes.   "If you want to suspect me or hate me, fine. But don't hurt Lydia. She's a good woman, not one of your toys."   That instinctive protectiveness finally gave me the answer I had waited two years to hear.   I looked at the call that had just ended on my screen and felt strangely relieved.   At last, I could free myself.