The "DC Universe: Rebirth" one-shot by Geoff Johns, Ivan Reis, Phil Jimenez, Ethan Van Sciver and Gary Frank ended with the major reveal that Alan Moore and Dave Gibbons' "Watchmen" characters, specifically Dr. Manhattan, were somehow involved in alterations in the DC Universe -- the first time a cast member of the seminal 1986-1987 miniseries had any type of interactions with DC's roster of characters.

As part of this revelation, Batman spotted The Comedian's blood-stained smiley face button -- one of the iconic pieces of "Watchmen" imagery -- in the Batcave. How it got there has remained a mystery since the "Rebirth" one-shot was released in May 2016, but it's set to be explored this late April and early May in a new four-issue crossover between the "Batman" and "The Flash" ongoing series, as DC Comics announced Thursday via press release.

Appropriately titled "The Button," the story will take place in "Batman" and "The Flash" #21 and #22, with the "Batman" issues by writer Tom King and artist Jason Fabok, and "The Flash" installments from writer Joshua Williamson and artist Howard Porter.

Here's DC's official description of the storyline: "Two greatest detectives in the DC Universe unite to unravel the mystery behind a certain blood stained smiley face button stuck in the Batcave wall. However, what begins as a simple investigation soon turns deadly when the secrets of the button prove irresistible to an unwelcome third party -- and it’s not who anyone suspects! This is a mystery woven throughout time, and the countdown starts here!"

Each issue of "The Button" will feature both a lenticular cover along with a regular cover, each drawn by Fabok. The lenticular cover editions will retail for $3.99, with the regular covers at the standard Rebirth price of $2.99.

Though the "Watchmen" reveal was arguably the biggest development of several in the "Rebirth" one-shot, follow-ups at this point have been limited to teases in select books of the "Rebirth" line, including "The Flash." Back in July at Comic-Con International in Dan Diego, DC Co-Publisher Dan DiDio told CBR that the "Rebirth" one-shot was the beginning of a two-year plan that's still playing out.

"When we went out and we set up Rebirth, we set up a two-year story," DiDio said. "A lot of the questions that are out there will be answered during that two-year plan. The goal is not to answer every question in the beginning, but to roll things out and continue to excite people all the way through. You’ll see a lot of twists and turns coming out over the next year or so that will get you to, hopefully, where you want to be."

Williamson is also writing the currently unfolding "Justice League vs. Suicide Squad" miniseries, which he told CBR in November will have ties to the "Rebirth"/"Watchmen" mystery.

"When people read the whole event -- it’s hard to talk about this because of spoilers -- they’re going to see it all adds up, and it definitely gives you a big piece of what we’re doing next year, moving forward with Rebirth," Williamson said.

Alan Moore has long made his stance clear that he doesn't endorse revisiting "Watchmen" in any form. DC's first major "Watchmen" follow-up was the "Before Watchmen" series of prequels in 2012 and 2013. The first part of "The Button" is scheduled for release on April 19 from DC Comics.