I took a married female good friend along as my guest to a work-related party last year, and one of my married male colleagues flirted outrageously with her, and when his wife came up (my friend had no idea he was married) he was rude to his wife and when the wife said she wanted to go home, he told her (right in front of us) to go away. This male colleague has a bit of a reputation (eg once had affair with very young new recruit whom he was managing, and male colleagues make jokes implying that he is unfaithful generally) but I never personally have had a problem with him, as I am very no-nonsense. He just gives me compliments on what I am wearing, and I say thank you frostily and that is that. I really don't know what is the extent of his infidelity, but definitely at least one affair and general gossip about him. His wife can be a bit stand offish with other women (wonder why!), but after a few years of knowing me, has become more relaxed, and although I don't know her well, I like her. I feel sorry for her because they have 3 kids and she has made career sacrifices for her husband, and he is disrespectful to her, although I don't know how bad the problem is. Anyway, after the party, my friend told me that he gone away and got her work phone number (where she worked had come up in their conversation) and left several messages for her to meet him for a drink. I warned her about what he is like, and she told me that she was not going to reply to him. Since then, all kinds of changes have happened and she is going through a very rough time, including getting divorced. I know that she is going through a really vulnerable and lonely period in her life. She told me that my work colleague has been in touch with her again. I told that I was sorry for being really blunt, but that I really didn't think it was right, because he is married, and I feel sorry for his wife, even if he is a philanderer and the wife tolerates it, and that I really didn't want him to take advantage of my friend at this time, because she really needed a friend, not someone like him. In a way it is nothing to do with me, but I feel involved because I introduced them, and I want to protect his wife, and I want to protect my friend from getting used by him. Is there anything I can do?