Orphaned by tragedy and raised by his best friend's father, brilliant CSI Barry Allen gains powers when lightning strikes him during a freak storm. When another meta-human attacks the city, Barry puts his powers to the test.

Getting to grips with life in the fast lane, Barry confronts a robber who can make multiple versions of himself.

As Barry and the team at S.T.A.R. Labs work to capture Kyle Nimbus (guest star Anthony Carrigan), a.k.a. The Mist, a dangerous new meta-human with toxic gas powers, they revisit the painful night the particle accelerator exploded and killed Caitlin’s fiancé, Ronnie Raymond (recurring guest star Robbie Amell). Meanwhile, Joe decides to finally visit Henry in jail after all these years, but things take a dangerous turn when Kyle shows up looking to punish Joe for arresting him years ago. Meanwhile, Iris and Eddie continue to hide their relationship from Joe.

A villain named Leonard Snart gets his hands on a `cold' gun -- which could kill Barry. Joe gives Iris the silent treatment.

After a bomb goes off downtown, the army, led by General Eiling (guest star Clancy Brown), rolls in and takes over the case, much to Joe’s surprise. Suspicious, Joe tells Barry that he and his friends at S.T.A.R. Labs should look into the army’s involvement. Wells informs the team that Eiling was experimenting on his men to turn them into super soldiers. Cisco confirms one of Eiling’s soldiers, Bette Sans Souci (guest star Kelly Frye), was at the bomb site. The Flash tracks her down and realizes that she’s not setting off the bombs: she is a meta-human who can blow things up just by touching them. Meanwhile, when Joe learns Iris is writing about “the streak,” he tells Barry to make her stop. Barry realizes Iris won’t listen to him so he decides to have The Flash pay her a visit.

The Flash faces a new meta-human named Tony (guest star Greg Finley), who can turn himself into girded steel at will. While Dr. Wells and Caitlin are concerned about Barry’s safety, Cisco comes up with a plan to take Tony (aka DC Comic villain Girder) down. Meanwhile, Iris’s blog on The Flash gets her into trouble, and Eddie witnesses Tony’s abilities firsthand and begins to ask questions that Joe doesn’t want answered. Joe asks Dr. Wells to help him solve Nora Allen’s murder.