The publishing world is abuzz with news that Michael Crichton, the bestselling author of science fiction thrillers such as Jurassic Park and The Andromeda Strain, left behind at least one finished novel and part of a second when he died of cancer last November.

HarperCollins plans to publish both novels over the next year and a half as part of a $30 million book deal Crichton signed in 2001.

But the prolific Crichton, who was married five times and also created the hit TV series ER, which ended a 15-year run this month, left behind another, even bigger piece of unfinished business: the fate of a son born three months after the author died.

The son, John Michael Todd Crichton, isn't mentioned in Crichton's will, but as an "omitted child" in legal theory, he may nonetheless be entitled to one-third of the writer's estate. The amount at stake is not known, but may well reach into nine figures: By one account, Crichton earned $100 million a year in his prime.

In a dramatic twist worthy of Crichton himself, his widow—Sherri Alexander Crichton, who signed a prenuptial agreement limiting her share of the estate—is seeking to be named guardian of her son's property. Success would essentially let her circumvent the prenuptial pact.

Crichton had only one other child, a daughter named Taylor Anne Crichton, whom he had with his fourth wife, the actress and screenwriter Anne-Marie Martin. Taylor is named in Crichton's will, which was filed in probate petition in Los Angeles on January 26—coincidentally, the day Taylor turned 20.

The will leaves Crichton's estate plan mostly a mystery: Like many celebrities and wealthy people, he put the "residue" of his estate—legal jargon for everything, essentially—into a family trust. (Documents for the John Michael Crichton Trust, unfortunately, are not public.)

Crichton's will consists largely of standard boilerplate language, but there are also some pointed instructions aimed squarely at his legion of ex-spouses. The first paragraph, for instance, makes clear: "I have intentionally omitted to provide for Anne-Marie and my other former spouses under the terms of this will."

Later on, there is a reminder of the prenuptial agreement he signed with Sherri in April 2005, and Crichton instructs his executor "to be bound by the terms" of that deal. So that, apparently, took care of the wives.

But what of the children? Taylor, named in the will, is also listed as one of the beneficiaries of the private trust. What she will get is anybody's guess. But as an "omitted child," two-month-old John stands to collect one-third of his famous father's fortune.

Crichton's family said the author, who was 66, died "unexpectedly" on November 4 after "a courageous and private battle against cancer." A long-time smoker, Crichton reportedly died of throat cancer, but the length of his battle with that disease—and whether he knew of his wife's pregnancy—are a mystery.