'The Flash' season 3 episode 8 spoilers: synopsis teases 4-way superhero crossover; heroes take on alien Dominators

It's heroes versus aliens in an epic crossover event in the upcoming episode of "The Flash" season 3.
Titled "Invasion!" the next episode will feature the much-awaited crossover between the heroes of The CW. According to the official synopsis, aliens known as the Dominators strike Central City. In an attempt to stop them, Barry (Grant Gustin) speeds over to Star City to ask help from the Green Arrow (guest star Stephen Amell).
However, the two heroes realize that the fight against the Dominators is bigger than they initially thought. The team expands as Green Arrow and the Flash are joined by the Legends of Tomorrow. Additionally, Barry and Cisco (Carlos Valdes) create a breach to bring back yet another secret weapon: Supergirl (guest star Melissa Benoist).
Once the superhero team is assembled, they must come up with a plan to attack. Just when they all think everything is running smoothly, a secret connected to Flashpoint is revealed and suddenly no one knows if they can still trust each other. Wally (Keiynan Lonsdale) is planning to join the fight against the Dominators but Iris (Candice Patton) tells him he's not ready.
Tuesday's episode saw Wally West (Keiynan Lonsdale) realizing that he was in touch with the speed force during "Flashpoint." As a result, Wally may now have the choice to fully embrace his fate as Kid Flash. Speaking with TV Guide, Lonsdale spoke about what how Wally's speedster ability will help him deal with his insecurity towards Barry.
"For Wally, if he feels like there's this uneven treatment, he's going to call it out," the actor said. "In terms, of getting powers, will that help him? Getting powers doesn't always change the person that you are. It can heighten certain qualities. That's something that Wally would have to, with or without powers, sort of deal with."
"The Flash" season 3 airs every Tuesday night at 8 p.m. ET on The CW.