The Flash
Pictured: The poster for the crossover special featuring Supergirl, The Flash, Arrow and Legends of Tomorrow.Facebook/The Flash

Season 3 episode 8 of The Flash will see Barry teaming up with Green Arrow, Supergirl and the Legends of Tomorrow to take down the aliens in the CW crossover special that will be aired live on Tuesday.

The episode is titled Invasion and it will see Barry reaching out to the Green Arrow when aliens called the Dominators attack Central City. The crossover kicked off towards the end of Monday's episode of Supergirl when Barry and Cisco came over to ask for a favour.

Meanwhile, the synopsis for Tuesday's episode titled Invasion hints at the superheroes dealing with trust issues when a shocking secret related to the future is revealed. The episode will also see Wally attempting to join the battle against the aliens, but Candice Patton's Iris stops him saying he isn't ready yet.

The synopsis for Invasion reads: "Barry asks Green Arrow for help when aliens attack Central City, but when they realize that won't be enough, they track down the Legends of Tomorrow so they can bring Supergirl in on the battle."

The previous episode of The Flash ended with the revelation that Tom Felton's Julian is Alchemy, but according to executive producer Andrew Kreisberg, there will be another villain who is yet to make his presence felt.

"There's a villain coming up who's another one of the husk villains that was created by Alchemy, so there's that to deal with, but the midseason finale kind of creates a new problem for our heroes that they weren't anticipating -- something that they've never faced before," Kreisberg said, according to

The Flash airs Tuesdays on the CW.