The biggest superhero movie in history, Avengers: Infinity War, is set for release on April 27. In what seems to be an effort to prevent spoilers from leaking beforehand, Disney has taken one giant security measure to ensure nothing is revealed before release: Preventing even its biggest stars from seeing the whole film for themselves.

That’s a good thing, too. Marvel’s stars are sometimes prone to reveal spoilers, many times by accident.

On Monday, Marvel stars Benedict Cumberbatch, Tom Holland, and Tom Hiddleston appeared as guests on ABC’s Good Morning America via satellite from London. This week, Marvel began the press tour for Infinity War in London, kicking off with a 20-minute preview screened for the first time. On the talk show, Hiddleston — who plays the mischievous anti-hero Loki, revealed that the London preview was the first time anyone from the cast had seen the film.

“None of us have seen the film and we’ll be seeing it at the same time as you guys see it on April the 27th, because there’s so much about the film that’s being kept under wraps,” Hiddleston said. “Last night was about 20 minutes and the first time I’ve seen it.”

Cumberbatch, who plays Doctor Strange, added: “We haven’t seen hadn’t seen the footage until last night, so we came out as fanned up as the fans. It was really, really excited.”

Cumberbatch had one advantage over his two co-stars, however. Revealing that Strange has a “wonderful” role in Infinity War, the star of BBC’s Sherlock was allowed to read the entire script for context.

“I had to sort of understand what the context was,” he said. “Strange has this wonderful role in it. I’m trying to hold the multiverse together, so I kind of needed to know what goes on between those brackets.”

Being that the Marvel films are some of the biggest movies on the planet, it’s understandable that Disney wouldn’t want plot details surfacing before release. But it’s one hell of a security measure to stop even the actors, who were on set for making the thing, to not even see the finished product for themselves. With this kind of secrecy, that has to mean at least one or two heroes will bite the dust, which will no doubt change the MCU forever.

Avengers: Infinity War will be released on April 27.