House had diagnosed Vincent with herpes and told him that he had to tell his wife so she could be treated as well. When Vincent denied ever cheating on his wife, House told him that his wife had to be cheating with someone and narrowed down the list of suspects to the children's karate instructor.
Charlotte confronted Lisa Cuddy saying she hadn't been sleeping with the karate instructor and, without being told, realized House was to blame for her anger. She ordered House to come to her office later that day to work out the differences between Vincent and Charlotte.
House arrived late and Cuddy was still trying to explain to Vincent and Charlotte there was no way of knowing which spouse caught it from the other. At that point, House told them both that one of them probably caught it from a public toilet seat. Cuddy knew that wasn't possible, but House spoke over her so she couldn't interrupt. Vincent said it was possible that he could have gotten it that way, but Charlotte thought House was mistaken. House realized Vincent was the cheater - as the guilty party he grasped at the straw he was offered to get himself off the hook. Charlotte turned her anger at Vincent and Cuddy realized that neither of them cared about what House had said and they wouldn't be bothering the hospital again.