Video: The Flash's Grant Gustin Previews 'Gut-Wrenching' Finale — Plus: A Killer Frost Forecast?

With The CW’s The Flash set to air its freshman finale Tuesday at 8/7, the forecast calls for lotsa action, much heartbreak and just mayyyybe a nasty bit of snow.

Speaking with TVLine at The CW’s Upfronts red carpet, Grant Gustin affirmed that catching Reverse-Flash aka Eobard Thawne, and besting the rival speedster, are wildly different things.

“They’re going to have a face-to-face and monologue at each other for a bit, and he gets in Barry’s head,” the Flash star previewed. With Barry tempted to time-travel back to the night of his mother’s murder, the result is “incredibly gut-wrenching, heart-breaking,” he warns.

On the (possibly?) lighter side, promos have also hinted at a wedding between S.T.A.R. Labs’ Caitlin Snow and fiance Ronnie, who as a metahuman now exists as half of the Firestorm entity. “There’s a huge crisis in the finale, it feels like the world could end, so Caitlin is reaching out for some stability in her life,” Danielle Panabaker told TVLine. Alas, it sounds like a new player — Caitlin’s fated alter ego, Killer Frost — could throw cold water on any honeymoon for the lovebirds.

“I think you’ll see a little something in the finale…,” Panabaker hints with a smile, adding that she’s been “dying” to explore the good doctor’s villainous alter ego. “I cannot wait!”

All told, Carlos Valdes, who plays Cisco, echoes that which Candice Patton told TVLine, that The Flash’s Season 1 closer is “very unexpected…. It’s somewhat of a different color than what I thought it would be.” Which is not necessarily a bad thing. Says Valdes, “I think it might be the best [episode] we’ve done thus far.”