Law & Order: Criminal Intent: Season 4, Episode 12

4 - 12: Collective

After police accidentally shoot to death an innocent collector of expensive toys, Detectives Goren and Eames discover that the victim might have fallen prey to a conniving vixen who trolls sci-fi and vampire conventions in sexy outfits looking for lonely men who have massed rare and valuable collections desired by cult-like fans. The detectives attend a costume ball for fans of a "crypt club" and find a death-obsessed secret society -- some of whom could be responsible for a real murder.