As the writers of Avengers: Endgame, out on Friday (April 26), the duo has been working on the climax to phase three of the Marvel Cinematic Universe since 2015. It’s the 22nd film in the saga (they’ve written six of them). When Avengers: Infinity War came out this time last year, it set up a story that would cap off a decade of stories and encompass a huge cast of A-list celebrities. But they couldn’t talk about it.

“For all the people talking about it on the internet, we are off, burrowing away at this thing, but no one really knows about it,” said Markus, M.A. ’96.

“It’s so secret,” added McFeely, M.A. ’96.

So opening night, they said, is gratifying. That’s when they traditionally ride around Los Angeles in a van with directors Anthony and Joe Russo, producers and a few actors. They’ll pop into theaters to surprise excited moviegoers.

“To be in a room full of people about to see the thing finally is very pleasing,” said Markus.

They tackled Infinity War and Endgame at the same time. After shooting Captain America: Civil War, they got to work writing both films. It’s a process they’ve honed after more than 20 years as a team — and involves extensive outlining, individual writing of scenes, and then rewriting together.

And for the culminating stories, they had to make room for many superheroes. The Infinity War posters featured 23 characters, including Iron Man (Robert Downey Jr.), Thor (Chris Hemsworth), The Hulk (Mark Ruffalo), Black Widow (Scarlett Johansson) and Captain America (Chris Evans). Fitting them into a coherent story posed a new challenge for the writers.

“We learned some writing lessons, for sure,” said McFeely. “We couldn’t be indulgent. Every scene needed to do a couple different things. And characters couldn’t come in before the story absolutely required them, otherwise it’d be an 18-hour miniseries. It forced us to think about the story in very lean terms.”

Still, he said, Endgame comes in at about three hours.