'The Flash' Sneak Peek; The Flash Battles The Mist on Tonight's New Episode

Grant Gustin stars as Barry Allen in The Flash.

The Flash battles The Mist, and Caitlin tells Barry about Ronnie in this week's new episode of The Flash, airing at 8 p.m. ET/PT on The CW.

As Barry (Grant Gustin) and the team at S.T.A.R. Labs work to capture Kyle Nimbus (guest star Anthony Carrigan), a.k.a. The Mist, a dangerous new meta-human with toxic gas powers, they revisit the painful night the particle accelerator exploded and killed Caitlin's (Danielle Panabaker) fiancé, Ronnie (guest star Robbie Amell).

Meanwhile, Joe (Jesse Martin) decides to finally visit Henry (John Wesley Shipp) in jail after all these years, but things take a dangerous turn when Kyle shows up looking to punish Joe for arresting him years ago. Meanwhile, Iris (Candice Patton) and Eddie (Rick Cosnett) continue to hide their relationship from Joe.

Watch a sneak peek below: