Kara will be in grave danger in the upcoming episode of "Supergirl" season 2.

Based on the synopsis for episode 8, the evil CADMUS scientist, Lillian Luthor, will unleash the virus Medusa to attack every alien on the planet. In order to ensure everyone's safety, Kara will be forced to turn to Lena for help.

"Eliza comes to town to celebrate Thanksgiving with her daughters. Alex decides it's time to come out to her mother; Kara is shocked when Eliza suggests Mon-El has feelings for her, and Winn and James 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," reads the synopsis by Cartermatt.

The epic superhero crossover kicked off in last week's episode, when Barry Allen and Cisco Ramon sought Kara's help with an alien invasion on Planet Earth.

It can be recalled that in episode 7, Cyber Superman tried to retrieve Project Medusa, a virus created by Lillian to eliminate aliens because she perceives all of them as threats. Following Lux's imprisonment, she was blinded by her feelings so she wanted to exterminate all non-humans.

The upcoming episode is going to be a Thanksgiving special but will not be a regular holiday celebration. According to reports, it will not end with Kara putting an end to Project Medusa but it will kick-start the four-night crossover in the network.

"Supergirl" season 2, episode 8 airs on November 28, 8:00 P.M. on The CW.