Baby sitter

my wife told me about something that happened to her when she was in her twenties that always makes me horny,she used to baby sit regularly for a couple , she worked with the guy and had always fancied him, anyway one night the couple came home and the wife immediately took herself off to bed, the guy stayed up and was chatting to helen, he ended up making a move on her to which she responded, she said he pulled off her jeans and pants and mounted her on the sofa, as he was fucking away at her helen said she opened her eyes to see the wife standing in the doorway, she jumped away from the guy but he said ..its ok my wife is fine with it...helen said she felt embarrassed but let the guy slip his cock back in , the wife sat down in a chair and spread her legs and started wanking off watching helen and her husband fuck, my wife said this really turned her on and started giving the guy the fuck of his life, she said she got on top of the guy and was thrilled at the thought that the wife was watching as she sank herself onto the husbands cock..he pulled helens arse cheeks apart and fucked her for all he was worth. my wife said that the thought of his wife being able to see her cunt being fucked was mind blowing... helen said she heard the wife start coming from wanking herself that drove helen over the top and she herself came over the husbands cock, while he after a few more thrusts was shooting his cum up her...the wife got up and left the room as helen and the husband got dressed, before my wife left london she said they repeated it a few more times , but the wife always just sat there and wanked she never joined in