During his panel at Comic-Con International: San Diego, Geoff Johns confirmed that Dr. Manhattan is, in fact, the catalyst behind the stolen time revealed in DC Universe: Rebirth #1.
"If there's one being out there that could mess with time in such a radical way and challenge hope, it's Dr. Manhattan," said Johns.
As for why it wasn't revealed outright sooner, Johns said he didn't want it to overshadow the book's other big return.
"I wanted people to come away from DC Universe: Rebirth #1 talking about Barry and Wally and not be overshadowed by Doctor Manhattan."
"Did we just say Doctor Manhattan?" Dan DiDio interjected. "That's the first time we've officially confirmed that."
After that, Johns shared several panels from Doomsday Clock by Gary Frank.
The first was a new character in a prison cell. The next several was of a jailbreak and an abandoned car, which Johns relates to "desperation."
Although it hasn't been disclosed how many issues Doosmday Clock would be, Johns said that when the final issue comes out the other DC Universe titles will be caught up to the finale, and will segue into the future of the DC Universe.
"[Gary and I] are trying to do something we've never done before," said Johns.
The next panels are of a skull X-Ray, The Daily Planet, and Dr. Manhattan's atom symbol.
"I didn't want Dr. Manhattan to show up just as a gimmick or a cameo," said Johns. "There are people out there who believe the Watchmen should never be touched. But I have a story and I believe in it."
Johns said fans would know on the first page of the story what the whole thing is about.
"There's so much great thematic and important stuff about what these heroes mean to us," said Johns. "That's what Doomsday Clock is about. It encompasses everything from Action Comics #1 to today."
Johns' favorite interaction was "seeing the smartest man from one world meeting the smartest man from another - and the smartest man in the DC Universe is Lex Luthor."
Johns stopped short of saying "Ozymandias" but he heavily implied it.
The image at above right was shown during the panel. Drawn by Doomsday Clock's Gary Frank, it features the Justice League standing, apparently, on Mars with Earth in the background.
Doomsday Clock is scheduled to begin in November.