Walter Kirn (Up in the Air) had no idea what he was in for when he agreed to deliver an injured dog to “Clark Rockefeller,” a gifted con man and murderer, and the subject of Kirn’s gripping Blood Will Out: The True Story of a Murder, a Mystery, and a Masquerade.

What questions did you ask yourself while writing?

There’s a lot of literature about the con man. Even The Great Gatsby is, in some way, about a sociopath—a guy who changed his name and deceived the world. But there hasn’t been any literature about the dupe. The mark. In all sustained acts of deception there is cooperation from the mark. I wanted to examine that side. We’re all more gullible than we know.

It’s hard not to admire Clark’s ability to spin elaborate stories on the spot.

This guy had craft and acumen like you wouldn’t believe. He could come up with a 10-minute, completely fabricated story merely by shifting his eyes slightly to the right and pausing for one and a half seconds. He was like a supercomputer for deception, like “Evil Google”: ask your question and before you finished typing or speaking, he’d have a florid, completely unverifiable, and sometimes delightful, lie.

Speaking of Google, the Internet, during the span of the book, was not as efficient or accurate as it is today. Do you think Clark would be able to fool as many people now?

My book covers 1998 to 2008. In that time, Google and the Internet rose to fierce prominence. To Clark, that must have been like the approach of dawn to Dracula. It was through a Google search that he was undone. He told his wife that his mother was an actress—a real actress—who was dead. Her father did a search and found out this actress was still alive and told his daughter. That’s when things started to come apart.

You refer to him as “my friend,” even in the final pages. Do you consider him a friend?

There’s a tinge of irony in using that word, but yes, I did. When I was going through painful times after my divorce and he was going through painful times with his, we spoke heart-to-heart. Missing our children. Anger and frustration with our ex-wives. Sadness around the holidays without our families. That’s what real friends talk about. But I don’t think he told me one true thing now that I think of it.

Have you spoken with him since the trial?

I spoke to him on the day he was sentenced to life in prison. He came to court with about 500 handwritten pages; he was going to re-try the sentencing hearing. The judge denied his request. Clark didn’t really lose when he was convicted of murder; he lost when people stopped listening.