The featured speaker in 2008 was astronomer Neil deGrasse Tyson, now the host of Cosmos, the update of Carl Sagan’s classic miniseries. Christopher Hitchens spoke that year, and the illusionists Penn and Teller, heroes to the freethought movement, performed. Yet one of the biggest draws was Michael Shermer, a swaggering historian of science who, after an earlier career as an ultra-long-distance bicyclist, founded Skeptic magazine. He now contributes columns to Scientific American, speaks all over the world, and writes popular books like Why People Believe Weird Things, which are just what you should give to a friend who needs to be deprogrammed from a belief in fundamentalist Christianity, alien abduction, or bogus homeopathic remedies. He is a freethought celebrity, an exciting person for a young activist like Alison Smith to bump up against — which she did, at an after-party on the first night.

“I ran into Shermer in the hallway," Smith said recently, speaking publicly for the first time about what happened that night. They began talking, and he invited her to a Scotch and cigar party at the Caesars Palace hotel. “He was talking about future articles we could write, and he mentioned this party and asked if I could come, and I said yes.” At the party, they began downing drinks. “At some point,” Smith said, “I realized he wasn’t drinking them; he was hiding them underneath the table and pretending to drink them. I was drunk. After that, it all gets kind of blurry. I started to walk back to my hotel room, and he followed me and caught up with me.”

On their way from Caesars to the Flamingo, where they were both staying, she chatted briefly with a friend on her mobile phone, she told me. They got to the Flamingo. “He offered to walk me back to my room, but walked me to his instead. I don’t have a clear memory of what happened after that. I know we had sex.” She remembers calling a friend from an elevator after leaving his room. “I was in the elevator, but didn’t know what hotel.”

Over the next couple days, word spread around the convention that they had hooked up — whether the rumors began with what she told people, what he told people, or what others oversaw, it isn’t clear. Shermer went into damage-control mode. He called the friend Smith had spoken with during their walk “and lied to him about everything,” Smith said. She heard later from “a couple other people” whom Shermer had called to intercept the rumors. Finally, Shermer sent an email, which I have obtained, to a fellow skeptic, who was one of the conference organizers, and, as it happens, the friend Smith called from her mobile phone the night before. The email is worth reading in its entirety, right down to its conclusion — a sly, Clintonian diminishment of Smith. “Thanks for a great TAM,” Shermer wrote to the organizer. “You did a super job organizing and running the show…” It continued: