When Central City is under attack by aliens called Dominators, Barry Allen asks for the Green Arrow, Supergirl and the Legends help in the Heroes vs Alien crossover event. Episode 8 is titled, Invasion! that airs this Tuesday (29 November) at 8pm EST on The CW Network.

The official synopsis for the chapter reads as follows:

When aliens called the Dominators attack Central City, Barry (Grant Gustin) speeds over to Star City to ask the Green Arrow (guest star Stephen Amell) for help in stopping them. Realizing the battle against the Dominators is bigger than they thought, they track down the Legends of Tomorrow, and Barry and Cisco (Carlos Valdes) create a breach to bring back a secret weapon – Supergirl (guest star Melissa Benoist). Once all of the super friends are assembled, they come up with a plan to attack but a shocking secret related to Flashpoint is revealed and suddenly no one is sure who they can trust. Meanwhile, Wally (Keiynan Lonsdale) wants to join the battle against the aliens but Iris (Candice Patton) tells him he's not ready.

Click here to watch The Flash season 3 episode 3 live via The CW app. You can also watch the episode online by clicking here (only in the US).

The crossover kicked off with this Monday's (28 November) Supergirl episode, with Barry and Cisco arriving in Kara Danvers's Earth asking for her help. The second part will kick off in this Tuesday's The Flash episode where Barry will introduce Supergirl to the rest of the heroes team.

Melissa Benoist, who plays the Girl of Steel in the CW series, spoke to Comic Book about the crossover event. "It's really exciting to have everyone in one place. I think we're all really proud of our shows. It's a weird feeling to be in a room with bunch of people wearing superhero outfits and it's not like a costume party. It was a cool feeling. And it was basically everyone — everyone, there's so many people," Benoist said.

The 28-year old actress revealed that it was fun to film the scene. "I can't wait for people to see it, but I also was excited to fly in front of everyone. There were a few really awkward attempts, so I did kind of fall on my butt a little bit in front of everyone. But it was a fun; It was a supportive atmosphere."

DC crossover
Stephen Amell as Oliver Queen, Melissa Benoist as Kara/Supergirl and Grant Gustin as Barry Allen The CW/ Warner Bros TV