DEAR ABBY: I have a friend, “Karen,” who was once married to “Zack.” They divorced and went their separate ways, but nine years later they are back together. I am almost certain they have not remarried, although Karen uses his last name and refers to him as her husband.

Abby, Zack is a compulsive womanizer, always on the lookout for a sexual encounter. Karen doesn’t talk about it and pretends that everything is great with her and her “marriage.” We all pretend along with her, although picking up strange women for sex is dangerous in many ways.

I live on the coast, and a few weeks ago I drove south to a resort city to spend the weekend with a friend. As we sat in a restaurant, I noticed Zack leaving. (I don’t believe he saw me.) I mentioned to my friend and an acquaintance of hers who was sitting with us that I knew the man who was walking out. The acquaintance laughed and said most of the women in the area knew him. It seems he owns a condo there and has attracted some attention because of his behavior. I said I knew about his womanizing. She replied, “Yes, but are you aware that he picks up men as well?” I was stunned.

The person who gave me the information seemed sure of what she was saying, and gave me enough details to convince me that Zack is picking up men for sex as casually as he does women. I am afraid he is exposing Karen to HIV, and I’m almost positive that she doesn’t know about his attraction to men.

Should I go to Karen and tell her about this? I’m afraid of losing her friendship if I say anything, but if I don’t and something terrible happens, I don’t think I could forgive myself. Please advise. – BITING MY TONGUE IN N. CAROLINA

DEAR BITING: Although I do not endorse repeating gossip, a case such as the one you have described is an exception. Your friend should be told immediately about your visit to the nearby city, that you saw the man she calls her husband there, and what you were told. She should also be advised to see her doctor and be tested for every sexually transmitted disease there is a test for – if she hasn’t done so already.

Please make clear that although you were worried about losing her friendship if you came to her about this, you were more worried about her welfare. What happens after that is her decision, and your conscience will be clear.

DEAR ABBY: I have two teenage stepsons living with me and their mother. The older boy, “Jake,” who is 16, wants his mother to take him and his brother out once a week or so to be alone with her, while excluding me and my daughter. Jake is very shy and an introvert. I feel that this is contrary to the common good and will promote a lack of trust in the home.

However, I love my girlfriend very much and will do anything to keep her happy. Am I wrong for feeling betrayed over this? – STEPFATHER IN MASSACHUSETTS

DEAR “STEPFATHER”: Unless I have missed something in your letter, you and the boys’ mother are not married – which makes you a caring live-in, but not a spouse or stepdad. I do not regard Jake’s wanting alone time with his mother as any threat to you. As a matter of fact, it might be a good idea for you to schedule private time with your daughter while the boys are with their mother. This is not a betrayal or rejection of you, and you should not feel insecure about it.

Dear Abby is written by Abigail Van Buren, also known as Jeanne Phillips, and was founded by her mother, Pauline Phillips. Write Dear Abby at www.DearAbby.com or P.O. Box 69440, Los Angeles, CA 90069.