Invasion kicks off tomorrow night Monday, November 28th at 8pm ET with Supergirl as the aliens known as the Dominators make their way to Earth starting war over the metahumans.
Supergirl "Medusa" Invasion episode synopsis":
A NIGHT OF CONFESSIONS; THE EPIC SUPERHERO CROSSOVER KICKS OFF TONIGHT — Eliza (guest star Helen Slater) comes to town to celebrate Thanksgiving with her daughters. Alex (Chyler Leigh) decides it’s time to come out to her mother; Kara (Melissa Benoist) is shocked when Eliza suggests Mon-El (Chris Wood) has feelings for her, and Winn (Jeremy Jordan) and James (Mehcad Brooks) consider telling Kara the truth about the Guardian. Meanwhile, CADMUS unleashes a virus that instantly kills any alien in the vicinity so Kara enlists an unexpected ally – Lena Luthor (Katie McGrath). The epic superhero crossover kicks off tonight when Barry Allen (guest star Grant Gustin) and Cisco Ramon (guest star Carlos Valdes) seek Kara’s help with an alien invasion on their Earth. Stefan Pleszczynski directed the episode written by Jessica Queller & Derek Simon (#208). Original airdate 11/28/2016.