Perseus and Andromeda (Leighton) daughters of Poseidon, the god of the sea. When the nymphs became aware of her claims, they protested to their father, who retaliated by calling up a sea monster called Cetus to patrol and wreak havoc along the coastline of Ethiopia placing Cassiope's kingdom at risk. In response the Queen, together with her husband Cepheus, decided to sacrifice her daughter, Princess Andromeda, to the monster. Andromeda was chained to a rock at the edge of the sea as an offering to the monster. Perseus was travelling back home on his winged horse, Pegasus, after battling with Medusa. He rescued Andromeda
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.