Barry and Iris saw a zombie movie and she admits she is interested in the red streak. She tries to show him a photo and it's Eddie. Barry runs off to stop some bad guys and is back before she's off the phone. And he's famished!

They walk past a group of bambinos. The head dude asks for it to be closed off and someone breaks a key in the door just before the green mist overtakes them.

Barry has to watch cops brag about the arrest he helped them make.

Joe is ready to go through every scrap of evidence with Barry about the death of his mom.

Eddie is pushed aside while Joe talks with Barry about the gas having a mind of its own.

After they go to STAR Labs, Joe suggests the geniuses come up with a better way to keep super criminals so they don't have to execute every one they come up against. Cisco thinks the particle accelerator would be perfect, sending Caitlin off into her memory of the night it blew and she lost Ronnie.

Caitlin and Ronnie are talking about their honeymoon and arguing Tahiti and Mai tais versus Italy and pizza and wine.

Harrison prepares to launch the accelerator. Or something.

While they're clapping, Harrison pops some champagne and the liquid goes up out of the bottle and sits before dropping to the floor. Something is wrong.

Barry notices how uncomfortable Caitlin is at the prospect of going to the accelerator and Barry asks for her help with the gas.

Joe is watching old interrogation videos of Henry. Henry screamed at the cameras that Joe knows him, he's a doctor and could never hurt his wife, their kids are friends.

Eddie shows up and says he thought Joe was a the morgue. Whoops. Cisco shuts Ronnie inside. Harrison catches Cisco remembering the event and offers to talk if he ever needs it. Cisco ignores him.

Barry asks Caitlin what Ronnie was like. Ronnie was only there that night for Caitlin. She stops talking when saved by the gas results.

Barry goes after The Mist. He threatens Barry. He has one more name on his list, don't make me add you to it. And he goes inside Barry. Barry still manages to get back to the lab so Caitlin can not only get a sample, but save Barry. Cisco names The Mist.

Barry goes to Joe and says he doesn't understand. Joe understands more than he imagines and tells him about it.

Iris didn't tell her dad because it would then be real and something she could lose or screw up. They go public.

Barry tells Caitlin that even though his mother died 14 years ago, sometimes the pain is worse now than the day it happened. Barry accompanies Caitlin to the accelerator. She recalls Ronnie's last minutes. He set the parameters so the beam goes up and not out. The doors need to stay shut to protect her. His last words were "Caitlin, whatever happens...". Caitlin says he saved so many lives that day and nobody will ever know what he did.

They discover the identity of The Mist. The last person on his list of Kyle Nimbus will be Joe West. Joe is in Iron Heights seeing Henry. Caitlin reverse engineered an antidote to the toxin.

Joe tells Henry that now he knows Henry didn't do it. He's reopening the case and will find out who really killed his wife. He promises to get Henry out of there.

Nimbus shows up and tries to kill Joe. Henry witnesses it all, but perhaps not Barry's face. It was hard to tell.

Joe tells Iris and Eddie he knew about them and he's mad. He doesn't like complicated. He agrees not to shoot Eddie since Iris likes him.

Cisco and Caitlin talk. She loves Ronnie even more now.

Barry visits Henry. Henry tells him about the first time he walked. He ran because he had someplace to go. Right into his mom's arms.

Iris blogs about the streak.

Harrison is looking at The Flash suit. He flashes back to the night of the explosion. He enters his secret room to see what is happening with Barry as the explosion occurs. "See you soon, Barry," he says.