Barry (Grant Gustin) meets a potential ally on the upcoming episode of "The Flash" season 4.

Titled "Subject 9," next week's episode will see Ralph (Hartley Sawyer) find himself in serious danger. Barry continues his battle with DeVoe (guest star Sugar Lyn Beard), and he will meet a powerful woman who has abilities that could help him defeat his latest enemy.

After finding out that DeVoe is on the lookout for everyone who was aboard the bus, Ralph decides he no longer wants to be a hero. His priority has changed and his main concern now is staying alive. Meanwhile, Joe (Jesse L. Martin) gets some help from Harry (Tom Cavanagh) about his problem.

New photos from the episode show a new character meeting up with Barry. As seen in the previous episode, DeVoe is now taking control of Becky Sharpe aka Hazard's (Sugar Lyn Beard) body. Images from episode 9 confirm that their crusade will involve finding Izzy (Miranda MacDougall) — a genderbent version of the popular comic book villain The Fiddler.

Meanwhile, it has been previously announced that Iris (Candice Patton) will be a speedster in an upcoming season 4 episode. She will be essentially trading places with Barry, who will have to do Iris' job and stay at STAR Labs to manage the team. The first look at Iris' speedster costume shows a purple and white color scheme, which is somehow reminiscent of the Tornado Twins.

The said episode will see Team Flash cross paths with a new bus meta named Matthew aka Melting Pot (guest star Leonardo Nam). He has the power to swap people's DNA so during a battle with Team Flash, he moves Barry's super speed DNA to Iris. With a new threat on Central City, Iris will be squaring off against Melting Pot while Barry takes on the team leader mantle.

"The Flash" season 4 airs every Tuesday night at 8 p.m. EST on The CW.