"Supergirl" kicked off The CW crossover with its "Medusa" episode. Facebook/Supergirl on the CW

“Medusa,” the latest episode of “Supergirl,” kicked off The CW’s weeklong crossover with “The Flash,” “Arrow” and “Legends Of Tomorrow.” As expected, however, very little airtime was actually set aside for the beginning of the crossover.

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In the episode, Cyborg Superman released a virus in the alien bar, which affected those not originating from Earth. Mon-El was exposed to the virus and became ill. Meanwhile, Kara Danvers (Melissa Benoist) went to Lena Luthor (Katie McGrath) thinking the latter would help her track down Lilian Luthor (Brenda Strong). However, Lena did not initially believe Kara’s accusations.

Kara then figured out that the virus was created by her father. At the same time, Lena realized that her mother was behind Cadmus. Lena then double-crossed her mother by placing the isotope that neutralizes the virus in a bomb, which Lilian believed held the virus instead. Lilian is then taken by the police while Cyborg Superman disappears.

On a more personal note in “Supergirl,” Alex (Chyler Leigh) planned to tell her mother (Helen Slater) about her sexuality. However, a mysterious space rift derails her plan. Nevertheless, Eliza confirmed that she already knew about it and Alex and Maggie (Floriana Lima) shared their first kiss.

Supergirl and Mon-El also shared a kiss on “Medusa,” but it was just as the Daxamite was at death’s door. “You look beautiful with the weight of all these worlds on your shoulder,” he told her. But when he recovered, Mon-El told Kara he did not recall anything.

It is only at the end when audiences caught a glimpse of Barry Allen (Grant Gustin) and Cisco Ramon (Carlos Valdes). The two characters from “The Flash” enter Kara’s apartment via a portal from their universe. Barry then asks Kara if she is willing to return the favor he extended when the two last shared a mission.

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The CW Crossover continues with “The Flash,” “Arrow” and “Legends Of Tomorrow.” Australian audiences can catch the shows, along with “Supergirl” on Fox8.