S2, E8: Eliza Danvers (Helen Slater) 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 (recurring guest star Katie McGrath). Finally, the epic DC Super Hero Crossover Event kicks off 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.