Perseus (constellation) may be derived from the Babylonian Old Man (MUL.SHU.GI) constellation, then associated with East in the MUL.APINan astronomical compilation dating to around 1000 BCE. In Greek mythology, Perseus was the son of Danaë, who was sent by King Polydectes to bring the head of Medusa the Gorgon — whose visage caused all who gazed upon her to turn to stone. Perseus slew Medusa in her sleep, and Pegasus and Chrysaor appeared from her body. Perseus continued to the realm of Cepheus whose daughter Andromeda was to be sacrificed to Cetus the sea monster. Perseus rescued Andromeda from the monster by
Medusa (Supergirl) is raising suspicions about her. Hank Henshaw plants a device that unleashes smoke at the bar, which kills all the aliens inside except for Mon-El. Mon-El is placed in isolation and Eliza is brought in to figure out the toxin. The virus consumes Mon-El before Eliza determines it is Kryptonian. Kara determines Cadmus needed her blood so Henshaw could break into the Fortress of Solitude. Kelex regards Kara as an intruder and attacks; she learns Henshaw accessed the file on Medusa, a virus created for defense against potential invaders by her father. Eliza affirms her support for Alex coming out.