Technically speaking, the way I read the article, the threesome was moving along swimmingly. Things didn’t go south until it became a foursome.
Here’s what it sounds like: The woman who invited the people and the man who arrived home were cooperating and they planned to victimize the couple. If you read the entire thing that’s what it sounds like. Also, they were all seriously, seriously stupid, except for the lady who was asked to come over and help clean and then managed to escape. She might have been a little smarter.