# 2 looks to be the best of them. It sets the stage and keeps us in suspense. # 3 kinda goes clunk at the end. We know if he has discovered she took it that something will happen. But why the worry if the watch is a fake? I'd be more worried if it were real and she had stolen it.
#1 doesn't go far enough I think. If she were to find one of the victims and have suspicions about the man she is falling in love with it would ratchet up the tension.