When my son was a baby, I had a knock on my door and was asked by a very well spoken school boy (wearing the uniform of the local high school) if he could use my toilet. I foolishly let him and knew straight away I shouldn't have, my baby was having a nap in his room.
I stood at the bottom of the stairs, he was ages, then came out and dodged side wards onto the landing, I shouted its this way out, he came downstairs, thanked me and left.
I watched him, knock on other doors, he did gain entry to another house, I immediately phoned her, she outed him straight away.
Word went round the village, he'd done this a lot and was taking underwear to sniff.
Next incident, he impersonates the Doctors son, who he went to school with, was knocking on doors and doing a survey for his Dad, on women's sex life and periods. I think he was quite successful at gaining info, but one woman phoned the Doctor, complaining. The doctors son was hauled out of school by him and taken to the complaining woman's house. She confirmed it wasn't the same boy, but they quickly realised which schoolboy it was.
Police were involved and the family left the area.
I can't remember his name but I'm sure in later life, he would be a sex offender.