I’m writing with a dilemma that has left me shaken, confused, and torn. I’m a mother-in-law to a wonderful young man and my daughter, “Emily,” whom I’ve always been incredibly close to. Emily married “Dan” about five years ago, and from the outside, they seem to have a happy and thriving marriage. They have a beautiful little boy together and are planning to buy their first home. I’ve always liked Dan, and he’s been like a son to me.

Last weekend, Emily asked if I could stop by and pick up my grandson from their house, as she had to run some errands, and Dan was home working. I didn’t think twice. When I arrived, the house was unusually quiet, so I walked in quietly so as not to disturb my grandson if he was napping.

Then, to my horror, I heard voices coming from the master bedroom—Dan’s voice and another woman’s. I froze, but curiosity got the better of me. Peeking through the door, I saw Dan with a woman I didn’t recognize, both clearly in a compromising position. I immediately left, shaken, without alerting them to my presence.

Now, I feel trapped. Do I tell my daughter? Do I confront Dan? Part of me wants to scream at him, but I worry about the effect this might have on their marriage and on my grandson. I also dread being accused of meddling or ruining their family. If I don’t say anything, I’ll feel like I’m complicit in his betrayal. But if I do, I risk shattering their lives and losing my relationship with my daughter.

Please tell me: what should I do? How can I handle this delicate situation without doing irreparable harm?