By now I should know better. After all, it's hardly the first time this has happened. But when the phone rang and the desperate voice relayed the familiar sob story, I once again found myself unable to refuse playing the role of good neighbor.

The favor is always the same -- babysitting for a child whose mother works and whose regular sitter is ill/indisposed/exhausted. Occasionally there is a variation on the theme. The child's "slight fever" or "runny nose" disqualifies him from attendance at the day care center for the day, but does not make his parents any less indispensible from their jobs.

The underlying premise never varies. It is implied, sometimes expressed, and generally taken for granted.

"I didn't think you'd mind, unless you have big plans for this afternoon." There it is. A mother who doesn't work cannot in good conscience refuse to baby-sit for a desperate mother who does work, unless the former has "big plans" for the afternoon.

The disruption of little plans doesn't count. So unless I've been invited to lunch at the White House, I have little basis to deny her request.

Her thinking is: "I have so much to do, but what else has she got to do?" Working mothers I know apparently have decided that mothers who choose not to work owe something to the rest.

Before you conclude that I'm a crank who hates children, let me say that I was once a working mother. I know the panic of finding a substitute sitter when the regulr comes down with the flu 20 minutes before you're supposed to leave the house. And I know that the pressure not to let down one's colleagues or superiors can militate against taking the day off.

So when I hear a pleading mother's voice at the other end of the phone, old memories stir and I say, "No, I don't have any big plans."

What I feel like saying is that, while I may be the only mother in the neighborhood who doesn't work, that doesn't mean I'm the neighborhood mother. I also feel like announcing that by day-long freedom, which is as important to me as her job is to her, is not for sale at any price.

While I'm at it, I might suggest that she re-examine her priorities. But since ny philosophy is "assistance first -- advice later," I just say, "Sure, bring him right over."

By the time "Mom" comes to pick him up at the end of the day, my nerves are sufficiently shot to turn any attempted lecture into a tirade. So I hand the little tyke over to his mother and say as little as possible.

Lest you think I am the constant sucker, I'll admit to having said no on occasion -- the the friend who freely admitted her child had walking pneumonia, and to the mother who didn't want to wake "Daddy" up to mind his offspring so early on his day off. I think she was testing me to see if I knew a real emergency when I heard one.

So be forewarned, friends. Don't underestimate the importance of my day. Don't be surprised if I tell you next time that I couldn't possibly watch Jimmy today. I have big plans for the afternoon -- helping my son learn to ride a two-wheeler.

I heard that lunch at the White House is overrated anyway.