It's been 41 years since Louise Fitzhugh's book, Harriet the Spy, came out, prompting hundreds of young girls to slink around their houses, spying on family members and scribbling cryptic observations in secret notebooks.

By now, Harriet would be in her 50s, probably working some boring desk job, to the dismay of her many protégées.

But never fear: In publishing, what's old can just as easily be young again. And Delacorte Press announces that Harriet is back with a new spy adventure.

Harriet the Spy, Double Agent is slotted for release Sept. 13. Written by Maya Gold, it's based on the original Fitzhugh story. (That story spawned two sequels by Fitzhugh, and one by Helen Ericson in 2002, after the author's estate gave its permission for Ericson to draw on the heroine's popularity.)

This time out, according to the publisher, Harriet becomes friends with her new neighbor, Annie Smith. With three aliases to her name, Smith is the perfect spy recruit for Harriet. "But things begin to get a little sticky when Annie's pseudonyms appear to be a cover for something bigger than just an overactive imagination."

Harriet begins tailing her new friend. "And what she learns is quite startling - Annie is in love with an older man - a man old enough to be her father!"

That's a little racy for a book aimed at 10-year-olds, if you ask us. But, OK, we're willing to trust that somewhere along the way, Gold will relieve our anxieties about this May-December liaison.

Meanwhile, parents might want to keep the bedroom door locked. With Harriet back, there's no telling where the youngsters are hiding.