Every other Tuesday, Steven Petrow, the author of “Steven Petrow’s Complete Gay & Lesbian Manners” (Workman, 2011), addresses questions about gay and straight etiquette for a boomer-age audience. Send questions for Civil Behavior to stevenpetrow@earthlink.net.

Q. Dear Civil Behavior: I am going on a five-city tour overseas with a longtime friend of mine who happens to be gay (I am straight). Another old friend lives in one of the cities we’ll be visiting, and she wants to meet up and show me around. But she’s not that open-minded about gays (she knows he’s gay), so I’d be spending the day with her alone. How can I tell my travel companion I’m taking a detour to see an old friend but he can’t come? It’s really a dilemma for me. Any advice is greatly appreciated. — Terrado, age 61

A. Let’s start with Travel Etiquette 101: When traveling with friends, especially in midlife when we all have our idiosyncrasies, you’re free to agree on any ground rules at all – as long as you set those rules before your departure. And agreeing at the outset to take some separate excursions (you hate museums; he loves them) is perfectly acceptable. After all, going on a vacation together doesn’t mean you’re joined at the hip.

But let’s move on to Advanced Travel Etiquette and the “dilemma” you posed. The principle here is simple honesty. So although you could simply say (as one poster suggested when I posed your question on my Facebook page), “I have a friend in city X and I would like to spend time with her alone,” that’s not exactly true. Not to rain on your parade (or your vacation), but that little white lie is really a self-serving justification to get you out of this pickle. By omitting the salient fact that the friend you’re going to visit is not “gay-friendly” and does not want your companion to participate, you have, at best, distorted the situation (some might say you’ve done worse).