The upcoming episode of "The Flash" season 4 will feature an epic crossover event involving heroes and aliens.

Titled "Invasion," "The Flash" season 4, episode 8 will see the much-anticipated crossover between the heroes of The CW.

The official synopsis for the episode reveals that the Central City is invaded by aliens known as the Dominators. As Barry tries to stop them, he speeds over to Star City to seek the help of Green Arrow, to be portrayed by guest star Stephen Amell. Unfortunately, the two heroes will realize that fighting the aliens is not that easy. Hence, they will expand their team by teaming up with the Legends of Tomorrow.

Barry and Cisco, played by Carlos Valdes, will also create a breach in order to make possible the return of Supergirl, played by guest star Melissa Benoist.

As soon as the superhero team is already complete, they will try to come up with a plan to take down the Dominators. However, just when they all think that everything is going well, a secret associated with the Flashpoint is exposed, suddenly making it hard for each of them to trust each other. Wally will also plan to join the team in their fight against the aliens but Iris will stop him and tell him that he is not yet ready.

In the previous episode, Wally realized that he was in touch with the speed force during "Flashpoint." In the upcoming episode, viewers will know if he will finally embrace his destiny as Kid Flash.

"The Flash" season 4 airs every Tuesday night on The CW.