SPOILER WARNING: This article contains major spoilers for "The Icicle Cometh," the latest episode of The Flash.
Killer Frost is back! In "The Icicle Cometh," the latest episode of The Flash, the icy anti-hero made a dramatic return just in time to save Team Flash. She emerged when Icicle attempted to erase his alter-ego Thomas Snow once and for all.
By pretending to be Thomas, Icicle persuaded Caitlin to develop a serum that would "cure" his cryogenic mutation. Thanks to Cisco, they soon realized his nefarious intentions, but he used his cryogenic powers to stop them in their tracks. He stalled them long enough to make it to the Department of Defense, where he hoped to use their equipment to achieve a temperature of absolute zero so that the serum would work.
When Team Flash arrived at the DoD to stop him, they encountered temperatures rapidly approaching absolute zero. This stopped everyone in their tracks -- everyone but Caitlin, that is. She maintained homeostasis in the below-freezing temperatures, proving Killer Frost still existed within her. However, Killer Frost didn't emerge until Icicle attempted to inject himself with the serum. Using her ice powers, she knocked the serum out of his hands and crushed it under her boot. After a brief fight, he blasted her backwards and managed to escape.
Back at STAR Labs, Cisco was able to uncover the truth behind Killer Frost's disappearance. "All this time, we've been trying to figure out how Killer Frost disappeared, but we've been looking at it all wrong. We've been thinking DeVoe used Melting Point's powers, that he changed your metahuman DNA and removed Killer Frost from you, but tonight, you proved that she's still a part of you," he explained. "DeVoe used a different set of powers: Brainstorm!"
"All he did was create a mental block," Barry mused. "One you broke through tonight. So you can do that again. You've just got to learn how."
At that, Cisco dug up Harry's mental activity dampener, which the team used to defeat the Thinker last season. Realizing Cisco's plan, Caitlin said, "It'll help me hear her."
"It's my hope that the more you use it, the more you connect with her, eventually you won't need it anymore," Cisco explained. When he left the room, Caitlin placed the device on her head and heard Killer Frost speak to her for the first time since last season. This suggests she'll be able to call on Killer Frost for help moving forward this season.
At the red carpet event for The Flash's 100th episode, Danielle Panabaker -- who plays Caitlin on the series -- weighed in on what she believes draws fans to Killer Frost. "I think it's her strength. She's got a sort of wry sense of humor and she also doesn't play by the same rules as the rest of Team Flash," she shared. "Because she hasn't been there from the beginning, she kind of marches to the beat of her own drummer, so she's doing her own thing."
Airing Tuesdays at 8 p.m. ET/PT on The CW, The Flash stars Grant Gustin, Candice Patton, Carlos Valdes, Danielle Panabaker, Tom Cavanaugh, Jesse L. Martin, Danielle Nicolet, Hartley Sawyer, and Jessica Parker Kennedy.