Greg Boles, director of global-threat management for New York-based Kroll Associates, one of the world's largest private investigative firms, sees cause to worry when such incidents are revealed. "It could have a contagious effect," he warns. "Other people could get the idea and attempt a similar plot on someone else."

But what is the plot?

But then, what exactly is the plot? The FBI isn't saying what the threat was, who made it, when it was made or why Crowe was the target. It will not reveal whether it believes the threat was made by a hotheaded novice or a seasoned professional. "No arrest is imminent," says a security expert acquainted with the investigation.

While some security experts believe the recent publicity has made an attempted abduction of Crowe less likely, that doesn't mean that whoever made the threat has packed up and gone away. "If, in fact, the announcement has thwarted this kidnapping," says Patrick Mullany, former administrative agent in charge of the FBI office in L.A., "our thinking is always that, if it is a credible plot, the suspects will just switch targets."

-- JILL SMOLOWE -- NINA BIDDLE and PETE NORMAN in London, LYNDON STAMBLER, VICKI SHEFF-CAHAN, MICHELLE CARUSO, MEG GRANT, ELIZABETH LEONARD, KAREN BRAILSFORD, MARK DAGOSTINO and MARISA LAUDADIO in Los Angeles and Sandra Lee in Sydney