Brad Meltzer discusses new book ‘The First Conspiracy: The Secret Plot to Kill George Washington’

You never know where you’re going to find a conspiracy.

Author Brad Meltzer happened upon a huge one in one of the more mundane places — in the footnotes.

His latest book, a real-life thriller, “The First Conspiracy: The Secret Plot to Kill George Washington,” came to him while he was doing research for one of his novels — and even became a plot point in his 2015 page-turner “The President’s Shadow.”

“I was doing research on one of the thrillers and saw this little footnote,” says the Brooklyn-born author, who now lives in Florida. “It was something online because I remember clicking it and then clicking and clicking and clicking and I was down the rabbit hole.… I couldn’t shake it. And after five years, my rule is when something is still on brain after half a decade, that’s when you have to write the book about it. When you can’t shake it. And that’s exactly what I did.”

Co-written with Josh Mensch, the book chronicles a British attempt to kill then-General Washington in the very early days of the Revolutionary War. Imagine how history would have been different. And the plot is very much centered on New York City, with co-conspirators that included some very key figures in the city and state, including New York Governor William Tryon and Mayor David Mathews.

amNewYork spoke with Meltzer — who also writes the “Ordinary People Change the World” series of children’s books — about his latest release, in stores Jan. 8.

Tell us about NYC’s role in this story.

This is the ultimate New York story, right? This is George Washington. Everyone always thinks Philadelphia and you think of Concord and Lexington and Massachusetts. But New York was the place where it was all happening. And it was actually the New York archives and historical places that were the most helpful. … I like to imagine myself Indiana Jones and I play the theme song and then I’m running … and then I unearth some arcane detail. But the reality is, is in our interconnected world, all the information is there. Much of it is digitized, especially when it comes to George Washington. The problem is no one wants to read it. It’s just we’re too busy with other things. Josh and I, the only difference is we took the time to read it.

Which locations were key?

I think for us what came alive — when Washington found out [about the conspiracy], he built a gallows, hanged one of the co-conspirators in front of 20,000 people in what is now Chinatown. Twenty thousand people! The largest public execution at that point in North American history.

Are there any specific landmarks still around? What connections are there to this story?

Yeah, the book closes with all the landmarks. There’s obviously Tryon Park. … You can go to Tryon Park and you can see that. But I think one of my favorite things is we found … a marker for Mayor Mathews and he’s one of the guys who plotted to kill Washington. And there, up in, all the way up in Harlem, there’s a playground, and we’re able to find on this playground, among the paddleball courts and the slide and swings, there’s like a little plaque that honors two men. And one guy is someone we’ve never heard of, is not important to that story, and the other one is Mayor Mathews and it basically says like, what a jackass. [The plaque, with his name misspelled, says “Matthews was installed as the Loyalist mayor. Matthews was known as a thief, an embezzler, and a spendthrift”]. And it’s just great — it’s this tiny little plaque in the middle of nowhere.

Did any of the players in this story jump out at you?

John Jay. You’ll see John Jay as the master of espionage. We all know him as our first Supreme Court justice. But he’s this incredible counterintelligence officer, and our nation’s first, in fact. And you’ll see at the end of the book what the CIA does to this very day to honor him as such. None of which I knew until we started digging around on him and we’re like, he was this young kid in New York who was great at interrogation and kicking down doors and doing all those things that good counterintelligence officers would do today. But he was making it up during the American Revolution. So it’s just amazing to see what he accomplishes and what he spares the country from.

What else do you have coming up? I know you’re doing an animated series inspired by your “Ordinary People Change the World” books.

That’s not until November. But, yeah, “Xavier Riddle and the Secret Museum” is the title. And it’s basically Xavier, Yadina, his sister, and their dear friend Brad, who looks remarkably like someone who might be talking to you, who go on adventures. They have a problem in their lives here and they go back in time. They have a secret museum that takes them back in time to meet the heroes from our books. And they meet Abraham Lincoln and Amelia Earnhardt, you name it. And it’s in Christopher Eliopoulos’ amazing style, so I can’t wait for people to see it. And then in February we do “I Am Billy Jean King,” which is actually the newest book that comes out after this one.

If you go: Brad Meltzer will join co-author Josh Mensch at a book-signing event at Barnes & Noble Union Square at 7 p.m., Tuesday, 33 E. 17th St., more details at bn.com