1.3 Things You Can't Outrun (The Flash 2014)

Plot Summary
After a crime family is killed by a mysterious gas, Barry and Joe work to find the suspect, Caitlin works to find out how the meta-human and the gas are connected, and Cisco and Dr. Wells work on making a make-shift prison cell down at the particle accelerator.

During a run in with the metahuman, Kyle Nimbus, who had killed a judge in the mall, Barry gets into trouble after inhaling the toxic gas. He manages to run into S.T.A.R. Labs where Cisco, Caitlin, and Dr. Wells administer aid and at the same time, get a lung biopsy to analyze the gas. Barry reveals the metahuman can change into gas. While the investigation on the case undergoes, Barry learns about how Caitlin cannot move on from the death of her fiancé and how he sacrificed himself to direct the explosion upwards which saved countless lives.

When Kyle targets Joe who visited his father at Iron Heights Prison, Barry dashes over there to defeat Kyle.