This is a throwaway account. The relevant people are "the other man" who we'll call Dave (around 27-28) and couple: woman (around 19-20) and man (19). We'll call the woman Margret and the man Alvin.

I work in customer service and the team I work with are all friendly and get along decently well, with the usual hiccups. Two people (the couple) were hired onto the same team as Dave and I for some time and both got transferred to different departments. I do not necessarily get along with Alvin and find him quite annoying. I haven't gotten a chance to talk with Margret as she is usually quiet.

Around valentines day Dave showed up to work with hickeys. Multiple of varying darkness and size around his neck. It was clear what happened. Some time later I noticed that Margret was walking away from her department to talk to Dave. As everyone is friendly and always talking with each other I didn't want to jump to conclusions but thought it was odd and sudden, I did especially think it was odd that she only went to talk to him and not really anyone else. I did notice their age difference but I thought this person was friendly, as they were friendly with me as well. Dave had recently showed up to work again with a hickey.

Here is where I am afraid I may become an AH. If it is not evident Margret has Dave as a side piece. I have recently found this out from someone else, but they were told directly by Margret. Margret also told him that if at any point they got upset with Dave that they can tell Alvin about what was going on. I am not particularly friends or close with Alvin but I feel he has a right to know. Should I tell him and potentially risk a harsh work environment with Dave who is still on my team? Or should I mind my business and let them solve their own problems?

From what I have seen already the person who told me this information doesn't plan on telling Alvin unless prompted. Either way this unfolds I don't know how I can still be friendly with Dave after they have done something this immoral. Yes, this is none of my business and that is why I am hesitant to reach out to Alvin telling him about his girlfriend cheating as I am not close to him, don't know if he'll believe me, and I am not a part of this situation. What do I do?

PS: If this sounds similar to you, like you think this may be about you, no you don't and you didn't see this. Thank you.😊