Even though Doomsday Clock has only one issue remaining and Tom King's run on Batman is nearly over, readers haven't seen the last of "The Button." And the mystery of how Flashpoint's Batman made his way into the mainstream DC Universe stands to finally be revealed.King tweeted that the story arc will be referenced in Batman #84, his penultimate issue on the title. "The Button" was a 2017 four-issue crossover between Batman and The Flash co-written with Joshua Williamson. In the storyline, the two superhero detectives investigated the mystery behind Batman's discovery of The Comedian's iconic smiley-face button inside the Batcave.
Along the way, the storyline reintroduced the Flashpoint incarnation of Batman. In Flashpoint, young Bruce Wayne was killed and his father Thomas instead adopted the role of Batman.
The character has been integral throughout King's Batman run. Thomas Wayne has been one of Bane's key allies in Bane's quest to break The Bat. Prior to his reappearance in Batman, though, Thomas was last seen in "The Button" on the brink of death, along with the entire Flashpoint reality around him.
How Thomas survived his world's destruction, however, and made it to the mainstream DC Universe has never been revealed. King's tweets indicate that the mystery will be solved come the release of Batman #84.
Batman #84 has not yet been solicited for release.