In an ordinary day, Barry is forced to go through the motions of everyday life without his powers. In the meantime, Cisco tries to search for Zoom using Jay’s helmet. While they can see that Caitlin is fine, they have no way of tracking her. Furthermore, without Barry’s speed, they have no one who can travel through the breaches to Earth-2 or face Zoom for that matter, as reminded by Harry. Harry then leaves to track Jesse whom he found after a trail of cellular dead zones caused by a citizen of Earth-2’s different frequency. However, he has also found that there is another person from Earth-2 in Central City, and the group may be in danger. Joe encourages Barry not to listen to Harry’s complaints, but Barry instead goes to work in the lab. Although he’s still slow, he managed to finish his work in the morning. Without his speed, however, research is the only way he can stop crime.
Cisco: Is that why I'm always dropping calls around you?
Caitlin is still held captive in Zoom’s lair, though Jay swears he does not want to hurt her since he loves her. She rebukes him that he only cares about himself and that he no longer needs her since he was cured. He believes that she will eventually love him again so long as he keeps her captive. He unchains her but still keeps her trapped as he leaves. Caitlin explores the liar to find the man in the iron mask tapping on the wall. She exclaims that she doesn’t understand, only to be confronted by Killer Frost.
At the police station, Wally talks to Joe about the encounter with the Flash. Since Zoom said that Wally was important to someone close to the Flash, he easily deduced that Joe is friends with the hero. After the situation, he wants to thank the Flash for the rescue, but Joe does not fully agree to having Wally meet him.
Meanwhile, Harry tracks Jesse to a local apartment where her roommate lets him in, remarking that Jesse has never had any visitors. Harry confronts Jesse about coming back, but Jesse is just as stubborn about staying away from her father. She states that everything that has happened, the particle accelerator, the metahumans, and Zoom are all his fault. With a man like him willing to kill, she fears him just as much as she fears Zoom. Harry leaves with no results when he is suddenly stopped by a metahuman that crashes his van with his body. The man then kidnaps Harry. Barry and Cisco are then alerted to Harry’s crash and spot a man taking Harry. Despite not having his powers, and crime rates starting to rise because of it, Barry plans to examine the spot to find for clues. He calls Jesse to inform her on her father’s kidnapping and asks Iris for help to get to the scene.
Back at Zoom’s lair, Killer Frost and Caitlin talk to each other. Killer Frost also doesn’t know the identity of the man in the iron mask and cannot escape her prison of carbonite. However, she manages to convince Caitlin to work with her to escape. Without her powers, Caitlin has no hope of escaping the lair, and Caitlin is the only one who can figure out how to break the carbonite.
At the scene of the accident, Barry and Iris investigate the area. Iris notices that there are no obstacles or landmarks around, so a metahuman had to be responsible. Barry manages to find some DNA on the van, but they have no way of knowing whether the metahuman is from here or Earth-2, which means they have no idea what he would want with Harry. In an old amusement park, the metahuman reveals himself as Griffin Grey, a boy who was affected by the particle accelerator explosion. While he was gifted with super-strength, he also ages rapidly every time he uses it. Since he believes that Harry is Dr. Wells from Earth-2, Grey thinks that Harry can come up with a cure.
In STAR Labs, the team with Jesse gather to examine the evidence of Harry’s kidnapping. Through facial recognition, they are able to identify Grey, but local authorities state that he was a Central City High senior who went missing six months ago while the image is of an older man. While Barry was able to secure a blood sample from Grey, they cannot isolate his abilities without Caitlin’s expertise. Jesse, however, believes she can help since biochemistry was one of her five majors.
Cisco: How many majors do you have?
Jesse: Five. Is that uncommon here?
Iris: Girl, no. That is not common anywhere.
Caitlin works to free Killer Frost from the prison while asking her how she got her powers. Killer Frost says that she simply woke up affected by the dark matter, and the effect forced her to move back with her mother. The two women actually share a distaste of their mother as they consider her frigid and cruel. Killer Frost says she’s been like that since Charlie, her brother, died. Caitlin remarks that she never had a brother, but then she never understood why her mother was cold to her. She nearly completes a compound which will reduce the carbonite to nearly glass. Meanwhile, Wally confronts Joe again about talking to the Flash. Joe still refuses to let Wally meet the hero, but Wally implores him saying that being rescued for the Flash ultimately made him realize the risks he was giving himself. The fact that the Flash was willing to give up his powers was also the most noble thing anyone has ever done for him, and he wants to show his appreciation. Joe then says he will consider it.
The group track Grey’s movements to Ace Chemicals and plan to stop him there, though Jesse’s left behind in the lab. Barry, Joe, and Cisco corner the metahuman, but he uses his strength to toss nuclear barrels at the group. Barry attempts to stop him, but he gets knocked aside by a barrel. Before Barry is knocked out, however, he sees Grey age in front of him.
The team returns to the lair where they patch up Barry’s injury and analyze Grey’s abilities. According to Jesse, Grey’s cells are absorbing protein at an accelerated rate. While that gives him increased strength, it also causes him to age. The more he uses his strength, the faster he will age. Cisco then deduces that if they can get Grey to exert himself enough, they can eventually age him to become an old man. While they’re working out the technicalities, Barry questions his abilities without his powers with Iris. He recalls how Iris was the first person he saved, even before he knew what he could do. Iris reminds him that he can be a hero with or without his powers.
In the warehouse, Harry continues to mix a solution for Grey. Grey accuses him of thinking only for himself since he ruined so many lives with the explosion. Harry confides in him that he has a daughter while Grey reveals he had a girlfriend. With his condition, however, she no longer recognizes him. Grey warns that for his own sake, the solution must work.
Caitlin manages to break through the carbonite prison for Killer Frost. Before she can free the man in the iron mask, Killer Frost steps in and attempts to kill her. With Caitlin here, Killer Frost deduces that Zoom no longer needs her alive to remind him of the woman he loves. Killer Frost moves to strike Caitlin, but Zoom runs through Caitlin and proceeds to kill Killer Frost. He then warns Caitlin that if she tries to break out the man, he will die as well.
At STAR Labs, the group then plan to face Grey once again. Jesse and Cisco (with a little help from Felicity) create an armor for Barry’s suit made of the same dwarf star alloy as Ray Palmer’s ATOM suit. Unfortunately, they only had enough for Barry’s breastplate, and it can only take one punch from Grey. They also locate Harry in an old carnival warehouse, believing that they will also find Grey there. Barry, Cisco, and Joe then go to save Harry while Iris and Jesse monitor the action from their van. At that location, Grey begins to notice that Harry is simply diluting a solution without creating any sample. Before he can fight Harry, he spots the Flash outside and meets up with the hero.
With Iris and Jesse’s help switching on the carnival lights, Barry distracts Grey enough for them to fight. Grey gets one punch in, but Barry manages to stay on long enough for Grey to age rapidly. Finally, he falls to the ground dead but not before reverting back to his eighteen-year-old self. Jesse then rescues her dad. The group returns to STAR Labs where Harry and Jesse reconcile their differences. Harry remarks that since her mother died, he has vowed to protect her while Jesse understands since she was willing to do anything to save him after only losing him for one day. However, they do agree to give her some freedom for fear of going down that path again, and the two tearfully hug.
Joe then leads Wally to the roof of Jitters’ to meet the Flash. There, Wally expresses his gratitude towards the Flash and exclaims that his rescue has made him appreciate his life all the more for it. Meanwhile, back at Zoom’s lair, Caitlin berates the villain, saying that she only wants to return home. From that statement, he then decides that he will conquer Earth-1 just as he had Earth-2.
At STAR Labs, Barry arrives early to meet up with Harry. While they were able to take down Grey with Barry’s speed, Barry believes that there is no way he can face Zoom without it. Harry remarks that his encounter with Grey has made him more set on righting the wrongs that he caused, starting with getting Barry his speed back. The one way he can do that is to recreate the particle accelerator explosion.
- Griffin Grey is based off of a villain named The Griffin who was originally a friend of Bart Allen. He originally gained super-speed but, like his live-action counterpart, began to age rapidly until being overpowered by Bart.
- Ace Chemicals should sound familiar to some DC fans. The Gotham division was the same chemical factory that gave birth to the Joker!
- Tonight's episode features a reference not only to Felicity Smoak from Arrow but also Ray Palmer/The ATOM from Legends of Tomorrow.
- Caitlin may have had a brother, but what could have happened to him?