The Marvel folks were so serious about keeping anything and everything to do with "Avengers: Endgame" secret they went to extreme lengths to keep the script out of people's hands.
"There's only one draft of the full script and that's on an iPad that could be wiped with the press of a button," Avengers: Endgame co-director Joe Russo told news.com.au.
"And it's in a secure room and they have to come to the set to read it while someone is guarding the door."
If you think that means there's a conga line of actors standing outside for their turn to take in the whole story, you'd be mistaken.
Loose-lipped "Spider-Man" star Tom Holland revealed on the promotional tour for "Avengers: Infinity War" that he wasn't allowed to see the script or even know who he was fighting during a scene.
But it wasn't just the spoiler-prone Holland who was kept in the dark.
The number of actors who had full access to the script was "exceedingly limited", according to Joe.
Brother and co-director Anthony Russo said: "We will tell certain actors more than others but it's all based on what they need to know. That's really how we decide how much information an actor gets.
"It's reflective of their role in the film and what parts of the larger story their role intersects.
"To be fair to the actors, Joe and I, since the release of 'Captain America: Civil War' three years ago, have done nothing but work on these two movies full time for that entire period.
"The actors have worked on these movies, full-time, for perhaps a year out of that time, and that's depending on which actor we're talking about. When we wrap the filming, they go away and move on to other jobs.
"So they're not as immersed in this movie in the same way Joe and I are. It's maybe a little harder for them to remember where they're at, what they're supposed to say and what they're supposed to keep private. So we have a higher level of focus than they do."
Joe added that for three years they've both had to censor themselves in every conversation they've had with anyone not working on the movies, and that includes selective censoring during chats with their stars.
For them, keeping the surprises in "Avengers: Endgame" under wraps is pivotal.
"The movies that we viewed as children that an impact on us were movies that we had little context for, and the surprises unfolded in a theatre in front of us and we were emotionally invested that way," Joe said
"So now we're trying to give that same experience to audiences around the world and it's paramount to us that we preserve the integrity of that experience.
"We live in a culture that wants everything yesterday. And there are people who love to spoil things or are financially motivated to spoil things and we're doing to make damn sure they don't have the opportunity to do that."
Despite their best efforts, a few days after this interview, earlier this week five minutes of "Avengers: Endgame" footage, seemingly surreptitiously filmed during an early screening, was leaked online.
The directors took to social media to implore people to not spoil it for other fans.
"Avengers: Endgame" will pick up after the catastrophic events of last year's "Avengers: Infinity War", in which half the heroes were snapped out of existence alongside half of the universe's population.
What little we do know of the upcoming movie's plot from the trailers suggest the remaining superheroes, including Captain America, Thor and Black Widow, will mount a mission to reverse villain Thanos' actions.
The movie is expected to be one of the most financially successful releases of the year. It has already broken box office pre-sale records.