"Supergirl" kicks off The CW's four-way superhero crossover event tonight with The Flash (guest star Grant Gustin) coming over to seek Kara's (Melissa Benoist) help with an alien invasion on their Earth.

The episode titled "Medusa" may sound like quite a gritty episode but depending on how things unfold during the Danvers' Thanksgiving celebration, it might actually be a good one for the family. Eliza (guest star Helen Slater) comes to town to spend the holiday with her daughters. Alex (Chyler Leigh) starts contemplating on coming out to his mother like she did with her sister. Fans can only hope that the matriarch will be as understanding and be welcoming to her eldest like Kara was to her sister.

Meanwhile, the ever-observant Eliza alerts Kara to Mon-El's (Chris Wood) supposed romantic feelings for her which catch her off-guard. This is understandable given that the two National City foreigners did not exactly start off on the right foot. Their relationship was tumultuous in the beginning, but admittedly, they have both warmed up to each other. Elsewhere, James (Mehcad Brooks) and Winn (Jeremy Jordan) ponder on the idea of telling Kara the truth about the Guardian.

As for the weekly case at hand, Kara enlists the help of Lena Luthor (Katie McGrath) after CADMUS unleashes a virus that can instantly kill any alien within its affected vicinity.

By the end of the episode, the week-long thread of interconnected stories for DC's small screen universe will get its start when Barry Allen and Cisco Ramon (guest star Carlos Valdes) come to National City for Kara's help.

Benoist has talked briefly about the upcoming ensemble spectacle, saying, "There's a weird feeling to be in a room with a bunch of people wearing superhero outfits, and it's not like a costume party [feeling] ... it's a cool feeling" during a behind-the-scenes interview.

"There were few really awkward attempts," the "Glee" alum admitted. "So I did kind of fall on my butt a little bit in front of everyone, but it was fun. It was a supportive atmosphere."

"Supergirl" season 2 airs every Monday, 8 p.m. ET on The CW.