The fans are about to witness a role-reversal in the upcoming episode of the CW's "The Flash" season 4. The hit DC comic book series will feature an interesting development as the titular character, Barry Allen/The Flash (Grant Gustin) will lose his power to his own wife, Iris West (Candice Patton). For the first time, Iris will take on a superhero costume and use her newly obtained super speed to defend Central City.

The CW has released the promo teaser for "The Flash" season 4 episode 16. The upcoming episode, titled "Run, Iris, Run," will see Barry's wife assuming the role of the Scarlet Speedster as she accidentally obtained the powers of The Flash. It appears that the new metahuman in town, Matthew/Melting Pot (guest star Leonardo Nam), transferred Barry's super speed genes to Iris in an unexpected turn of events. Melting Pot is known for his ability to swap the DNA of people, to which he has done to Barry and Iris when Team Flash tried to confront him.

Now that Iris possesses the power of her husband, she is automatically bestowed the responsibility to defend Central City against anyone who wishes to destroy it. The timing of a mysterious new enemy's arrival in the city is just right for Iris to test her super speed. On the other hand, Barry, who is no longer a metahuman, will now do the task that his wife usually performs in Team Flash. As Iris physically engages the enemies in battle, Barry will serve as the team's leader.

Previously in "The Flash" season 4, Barry was able to save Central City from a nuclear threat after entering Flashtime. He would not be able to do it without the help of his fellow super speedsters from alternate dimensions, Jesse Quick (Violett Beane) and Jay Garrick (Teddy Sears). Of course, the threat posed by the season's big bad, Clifford DeVoe, also known as The Thinker, still remains.

"The Flash" season 4 episode 16 will air on Tuesday, Mar. 13, at 8 p.m. ET on The CW.