Back in June, word broke that Michael Keaton’s Batman will be appearing in The Flash movie. However, Keaton won’t be the only Dark Knight in the adaptation of DC’s Flashpoint event. Vanity Fair broke the story that Ben Affleck is set to reprise his role as Bruce Wayne/Batman for the first time since Justice League. Director Andy Muschietti also explained to Vanity Fair why getting Affleck back was so important to Ezra Miller’s Flash.

“He’s a very substantial part of the emotional impact of the movie,” said Muschietti. “The interaction and relationship between Barry and Affleck’s Wayne will bring an emotional level that we haven’t seen before. It’s Barry’s movie, it’s Barry’s story, but their characters are more related than we think. They both lost their mothers to murder, and that’s one of the emotional vessels of the movie. That’s where the Affleck Batman kicks in.”

Muschietti confirmed that Keaton’s Batman will have a “substantial” part as well. Regardless, Muschietti noted that bringing in alternate Batmen wouldn’t work without Affleck’s Dark Knight.