Barry Allen is fresh out of the police academy and his first case just so happens to be volunteering in Gotham during the blackout and oncoming storm. He gets paired up with Detectives Bullock and Spencer, and somehow ends up chasing down a junkie, high on a new drug called Icarus, which gives users the idea they have superpowers... aaaaand makes them spontaneously combust. As the three men try to put the junkie out in a back alley, a young Iris West, intern for the Gotham Gazette, appears out of a door sprays the man with a fire extinguisher.
Turns out the alley everyone is in behind a free clinic which is treating many people who've gone on Icarus benders, and Iris is looking into it for the paper. There seems to be a connection between Barry and Iris, but Bullock and Spencer beckon him away. While they transport the body, Barry concludes that whoever is selling the Icarus isn't whoever is making it, because it'd be bad business to sell a drug that has the high likelihood of killing the user (who's going to buy more?).
Once the three cops get back to the GCPD, Bullock tells Spencer to go be with his family, while he and Barry check out the free clinic Iris was at. As soon as they get there, a giant explosion goes off, and Barry, hardly thinking, goes into the fire to rescue Iris and as many people as he can. When the fire is put out, Barry believes he found trace elements of an accelerant, which means this just wasn't one of the junkies going up in flames, but Spencer and the other cops don't buy it, thinking they've got bigger concerns.
Barry doesn't let it go, and Iris sets him up with a makeshift lab where she's got a fridge of beer waiting for them. Barry asks how she kept the fridge working, but she reveals that her boss knows a fish merchant who gave them some bricks of ice. Barry then looks into a sample of Icarus Iris had gotten from the clinic, hoping to find out what it's made of, in hopes it'll lead them to a location. Turns out, there's a high amount of white phosphorus, which ignites when exposed to temperatures 86 degrees and up, so wherever it's being kept, the Icarus needs to be in a cold place... So Barry asks about this fish merchant Iris knows... Oh yeah, they almost hooked up, too. But things setting themselves on fire will sort of put a damper on the mood.
Sure enough, Barry and Iris find large batches of Icarus, they also find the fish merchant getting shot by the seller, who is Detective Spencer. Outside, Bullock arrives on a tip from Barry, and engages in a shootout with some of Spencer's men. Inside, Barry tries to fight off Spencer, who threatens Iris, but ends up getting dosed with Icarus. He tackles Spencer, but the Icarus starts to take effect, while Iris tries to find something to cool him down with. As Spencer goes for his gun, Bullock arrives, and shoots him, as Iris sprays Barry down with a refrigeration tube.
Sometime later, Barry and Bullock attend the funeral for Spencer and afterwards talk a bit. Barry asks why Bullock lied on the report, saying Spencer was shot on duty, to which Bullock tells him that not everything is so black and white. Spencer made some mistakes, and was trying to get some money to help his family, so this way, Spencer's family gets the life insurance and everything. With that, Bullock and Barry part, and before Barry catches his train back to Central City, he and Iris share a moment and their first kiss.