A new threat will greet the heroes of Central City in the upcoming episode of "The Flash" season 4. In episode 19, titled "Fury Rogue," Team Flash will have to deal with a meta human with powers so dangerous that he can wipe out all life in the city. With this, Barry Allen (Grant Gustin) will need the help of a friend from an alternate dimension, Leo (Wentworth Miller), also known as Citizen Cold.

According to the official synopsis of "The Flash" season 4 episode 19, Barry and his friends are having a problem with a meta known as Neil Borman (Alexander McDonald). Based on his ability to emit deadly level of radioactive materials out of his body, the character could be based on the DC comic book villain, Fallout. As the lives of innocent people are at stake in fighting the new enemy, the Scarlet Speedster will ask help from an ally in Earth-X. It appears that Leo's skill will come in handy in transporting the dangerous meta to a safe place.

Miller's character was first introduced in "Crisis on Earth-X" crossover event in the so-called "Arrow-verse," which includes "The Flash." Meanwhile, episode 19 will also feature another individual from Earth-X, but unlike Leo, this person has some dark motives. Siren-X (Katie Cassidy) is set to appear in next week's episode, and the villain will take Joe (Jesse L. Martin) and Caitlin (Danielle Panabaker) as her hostages. 

"The Flash" season 4 episode 19 is also expected to show the aftermath of the recent events, especially the shocking death of Ralph Dibny/Elongated Man (Hartley Sawyer) in the hands of Neil Sandilands/Clifford DeVoe. Team Flash may also have something else to worry about as Harry (Tom Cavanagh) has been acting strange after using his thinking cap invention. Based on the hints from previous episodes, it is likely that Harry has become the Reverse Flash, a villainous entity from earlier season.

"The Flash" season 4 episode 19 will air next Tuesday, April 24 at 8 p.m. ET on The CW.