Forensic scientist Barry Allen is struck by lightning and doused in chemical products that afford him superhuman speed, which he learns to control with help from Tina McGee, a scientist from S.T.A.R. Labs. Barry's brother, policeman Jay Allen, is murdered by his corrupt ex-partner, Nicholas Pike, the leader of a vicious gang of criminals.

Barry's secret identity is uncovered by Megan Lockhart, a private investigator employed by corrupt District Attorney Arthur Simonson, who blackmails Barry into becoming his secret accomplice in his efforts to bring legalized gambling into Central City on behalf of the organized crime.