1st printing. Collects Batman (2016 3rd Series) #21-22 and Flash (2016 5th Series) #21-22.

Written by Joshua Williamson and Tom King. Art by Jason Fabok and Howard Porter. Cover by Jason Fabok.

The explosive storyline is now available in trade paperback!

The Dark Knight and the Fastest Man Alive, the two greatest detectives on any world, unite to explore the mystery behind a certain blood-stained smiley button embedded in the Batcave wall. What starts as a simple investigation turns deadly when the secrets of the button prove irresistible to an unwelcome third party-and it's not who anyone suspects!

It's a mystery woven through time, and the ticking clock starts here!

Softcover, 7 1/2-in. x 11-in., 104 pages, full color.