The houseguest

Caroline and I sat talking on the back porch one Friday not long ago. A Manhattan apartment-dweller, Caroline calls her visits to my suburban home ''trips to the country'' and, toting a shocking-pink satchel, she usually shows up two or three times a year to spend one night.

This particular August night we were discussing a favorite topic - mysteries - because I was thinking about writing one. The black night outside was pierced frequently by lightning, and we sat by the flickering candlelight discussing plot development.

''How about this?'' said Caroline. ''A guest - could be an old college roommate - comes to spend a weekend and stays indefinitely.''

''Sure,'' I said, ''as her visit is about to end, she mentions she's hurt her ankle and can't leave. But ... she is neither limping nor wearing a bandage.''

''That's the idea. And then ... very slowly ... she insinuates herself into your household.'' Caroline went into the kitchen and returned with a plate of cookies. ''She borrows your clothes,'' she continued, ''because she'd only packed enough for a weekend, but, after a while, she's wearing only your clothes.''

The rain started and, with it, a chilly wind blew onto the porch. Caroline left again, and returned wearing one of my old sweaters. ''It's getting cold out here,'' she commented, taking another cookie from the plate.

''So we're talking about innocuous events, which start to take on ominous overtones,'' I said.

''Right. This guest does things under the guise of being helpful but she is, in fact, being very intrusive.'' She paused. ''Every morning she shows up at your bedroom door, knocks softly, and enters with a breakfast tray. At first, rather than hurt her feelings, you accept the tray, although the last thing you want is breakfast in bed. But this goes on, morning after morning. She, smiling sweetly, tells you she's just 'trying to help.' ''

I sat contemplating the imaginary prospect of having my furniture rearranged by someone else - small pieces at first, and then entire roomfuls - or of having my knickknacks moved around and, worse yet, disappearing altogether. I began to feel slightly uneasy. A booming clap of thunder splintered my thoughts.

''It seems to be getting nastier out here.'' I said. ''Why not call it a night and pick up the plot in the morning?''

''Sounds fine to me,'' said Caroline.

''By the way, what time tomorrow do you want to go back to the city?''

As we walked into the kitchen, Caroline took a can of soda from the refrigerator. ''Oh, didn't I tell you?'' she said, smiling sweetly as she popped the top. ''I don't have to be back until Monday morning. So, if you don't mind, I think I'll stay the entire weekend.''

A regular monthly column in the Book Review.