Back in 2002, Law & Order: Criminal Intent introduced Olivia d'Abo as the sinister Nicole Wallace (aka Elizabeth Hitchens). More than once, this homicidal hussy has proved an unusually crafty adversary for Vincent d'Onofrio's Detective Goren, who's got a soft spot for her. This Sunday at 9 pm/ET, NBC will let L&O: CI fans decide whether Nicole lives or dies. Say what?

Here's the sitch: The producers shot two endings for this week's episode, entitled "Great Barrier." Viewers east of the Mississippi will see one version, while those in the West will see the other. Both endings will be available for screening on NBC.com, where you're invited to vote for the one you prefer. The ultimate fate of Nicole Wallace will then be revealed on Oct. 24.

In pulling this stunt, series creator Rene Balcer says he's not mimicking the audience-participation element of reality shows. "With all due respect to reality TV, this idea predates that," he chuckles. "Sir Arthur Conan Doyle killed Sherlock Holmes in 1893 and then, with his readers in an uproar, he decided to bring him back a few years later. He did the same thing with his Moriarty character. So this is nothing new or exclusive to reality TV.

"What is new is that we're broadcasting the same episode on the same night with two different endings on different coasts," Balcer adds. "The only other time I can think that that happened was during the presidential election of 2000!"

L&O: CI didn't initially plan to give viewers a choice in Nicole's fate. The show shot one ending for the episode this past spring, then opted to shoot an alternative in August. "Both endings work," Balcer notes, adding that fan fervor over d'Abo's return (which NBC has been promoting) prompted him to get the audience involved. So which way does he think it'll go?

"Here's a woman you love to hate," he says. "She's a terrific nemesis. After 43 minutes, you might think, 'I'm gonna miss this character if she dies.' The audience may go into it thinking they want to kill her off, but the experience of watching the episode may change their minds."