Early Years EditBarry Allen's mother was killed when he was a child, with the blame wrongly placed on his father, who
was sent to prison as a result. Because of this, Barry became obsessed with forensic science, hoping to one day prove his father's innocence. One night, while working on his mother's case, Barry was struck by a bolt of lightning, which gave him the power to run at superhuman speeds.
Batman v Superman: Dawn of Justice Edit
At some point after obtaining his powers, Barry was caught on a security camera, stopping a man robbing a convenience store. The footage was later obtained by Lex Luthor.
The Flash later traveled back in time from a possible future to the Batcave. He appeared in a vortex of lightning, warning Bruce Wayne of the dangers regarding Superman, and that Lois Lane is "the key.
Justice League Edit
Barry was eventually approached by Bruce Wayne and asked to join a team of heroes he was assembling, in order to defend the Earth from an oncoming invasion. Barry eagerly accepted Wayne's offer without a second thought and joined him.