I was thinking of a story where a lady who is aged somewhere between 18 (near 19th birthday) to early twenties is feeling lonely and horny. One day she meets an nice and interesting man, they date for a while and despite her feeling that her new guy is keeping secrets she ends up sleeping with him. Not sure if the lady finds out or not but the guy she slept with is either a family member, a friend, or someone she thought of as an enemy or bully in school. He was able to disguise himself and a few times he mentions the movie The Saint and tv series it was based off of. He used a really convincing mask and wig that looked real. She also ends up pregnant. If she finds out who the guy was he tells her why he used the disguise and he cared for her and never meant to hurt her. She let's him know she did the stuff she did with him willingly and she loved it and him.