It was over dinner when it dawned on Matt that he might be having a threesome that night. He and his partner were out at a restaurant with her friend, another bisexual woman.
https://www.theguardian.com/lifeandstyle/2020/feb/11/threesomes-men-women-sex-psychology
https://www.theguardian.com/lifeandstyle/2020/feb/11/threesomes-men-women-sex-psychology