Help! I Think My Neighbor Is Up to Something Very Suspicious. Someone Needs to Warn His Wife.

Dear Prudence is Slate's advice column. I was browsing a men-seeking-men dating app when I came across the profile of my neighbor, "Gary." He described himself as "single and looking for fun." I happen to know that Gary is married with two kids under 3 years old. The thing is, I don't know his wife "Bethany" that well; we've only ever waved to one another in the neighborhood and briefly engaged in small talk when we run into each other.