The Flash Season 1 Episode 3 Things You Can’t Outrun
The whole gang is killed by green gas, Barry and Detective is investigating. They are talking about jail where they can keep all meta-human, they think the particle accelerator can be.
The green gas go to kill the judge, Barry found him and be attacked. Barry almost died but he can manage back to star lab, and get antidote.
The green gas try to kill detective, but Barry can safe him on time, Barry can out run the green gas until it exhaust, so he can knock him down.