He carries no badge. But Tom Voigt burns with the passion of a detective. Armed with just a computer, he is hellbent on catching a Wichita, Kans., serial killer, a strangler who has eluded the police for three decades. Voigt, 37, tall and bespectacled, crouches over his screen, sifting through the tips and theories zipped to his Web site. "These mysteries, they get to me," says Voigt, who forwards his clues to the authorities. When Wichita police arrested a man last week--and rumors flew that the killer had been snared, a notion that proved unfounded--the hits on his Web site soared to a million.

Voigt doesn't even live in Kansas; he's in San Francisco. And the tips he gets come from as far away as London and Amsterdam. Elsewhere around the Net, chat rooms and message boards buzz with theories about the Kansas killer, who, after a long silence, began taunting police and a local newspaper with letters and tantalizing bits of evidence earlier this year. Some of the theories are farfetched. But others hold a kernel of possibility. "Rojobahr," for instance, notes that the killer is believed to be 65 or 66 years old, and suggests: "What were the most popular baby boy names for the year 1939? I'll bet it's in the top 5."

America has always been obsessed with murder, and serial killers hold a special cult status in the annals of violent crime. But the rise of the Internet has given those fascinated with such slayings a place to indulge their crime-busting instincts in real time. Whether their myriad e-mails, IMs and postings actually help crack the case remains to be seen; law-enforcement officials warn that they can be overrun by helpful hints from the public. Wichita Police Chief Norman Williams says the flood of traffic and tips has, in some ways, "taken away from our ability to focus" on good leads. But then again, the Wichita police have kept secret crucial details about the case for some 30 years now, without making much headway in identifying the killer. Their decision last week to release a profile of the killer seemed a tacit acknowledgment that it takes only one break to solve the crime--even if it comes from the far reaches of cyberspace.

The Kansas serial killer, believed to have murdered eight people in the '70s and '80s, has certainly given the cops and the cybersleuths plenty to chew on. Claiming responsibility for the murders, a writer sent a letter to The Wichita Eagle in March. Enclosed was a photocopy of the driver's license of Vicki Wegerle, 28, a strangulation victim who police believe was his last victim, and pictures of a woman lying on the ground, apparently dead. The writer calls himself BTK, alluding to the style of his murders: bind, torture, kill. His first victims, in 1974, were Joseph and Julie Otero, their 11-year-old daughter and 9-year-old son--all found bound, gagged and strangled. A few months later he stabbed 21-year-old Kathryn Bright to death in her home. BTK struck again in 1977, killing two more. Two years later the killer waited inside the home of a 63-year-old woman, but left before she arrived. Later he mailed her a poem: "Oh, Anna, Why Didn't You Appear."

The police profile of the suspect was drawn from details in his letters. The killer was born in 1939. His father died in World War II, and he served in the military himself. He had a female acquaintance named Petra. It's possible, of course, that the real BTK is long dead. But police believe the details shared by the mysterious correspondent likely come from the killer.

Voigt greeted the newly released details like a kid at Christmas. As he sifted through the surge of messages to his site, he reflected on his role in the drama. "I'm like a filter," he says. "I've reached a lot of people, and the first thing they've told me is, 'I've never told this to the police.' It makes it all worthwhile when I hear those words." Another Web site invites the killer to respond. If he does, he could answer the 20 questions posted, such as "How do you want the game to end?" In Wichita, where people quiver in the darkness when they hear rattling outside their doors, they desperately want the game over.