The Flash Ruins Thanksgiving in Supergirl: Medusa Clip

Just as Supergirl, her family, James Olsen, Winn Schott, and Mon-El settle in for what promises to be an uneventful Thanksgiving dinner in Monday’s installment of Supergirl, some interdimensional radio static from The Flash and Vibe has to ruin everything.

In a newly-released clip from the episode, titled “Medusa,” Kara is toasted by both James Olsen — who seemingly wants to out himself as The Guardian before he’s not-so-subtlely talked out of it by Alex — and Mon-El before it’s finally time for the elder Danvers sister to speak.

Alex stands and, just before she can come out to her mother and those assembled, a breach opens up over their dinner table, startling everyone.

The other side of that breach, as we know, will be Cisco Ramon and Barry Allen, heading to National City to recruit Supergirl’s help against an invasion from the alien race known as the Dominators.

Here’s the official synopsis for the episode:

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 (Melisa 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.

Arrow, The Flash, and Supergirl will cross over with DC’s Legends of Tomorrow next week in “Invasion!” a three-part crossover that starts in the final moments of an episode of Supergirl and then plays through the other series. Based on the 1988 comic book event miniseries Invasion! from Keith Giffen, Bill Mantlo, Todd McFarlane, Bart Sears, and the crossover — with its marketing title “Heroes vs. Aliens” — will closely track the plot of that storyline: aliens will be assembled by The Dominators and descend on Earth to bring an end to the “threat” of Earth’s burgeoning metahuman community.

In the comics, the Dominion were secretly hoping to build their own super-race, and as a result created a handful of new superheroes in the course of the story.

In the TV version, rather than assembling a loose alliance of dangerous alien races, the Dominators will apparently be mind-controlling the aliens that join them. That’s a revelation that suggests even the heroes might be forced to take one another (or at least the alien Supergirl) on at some point in the story.

Supergirl airs Mondays at 8 p.m. ET/PT; The Flash on Tuesdays at the same time; Arrow on Wednesdays and DC’s Legends of Tomorrow on Thursdays. All four series air on The CW. The “Invasion!” crossover will air beginning November 28.