Supergirl

During the destruction of the planet Krypton, scientist Zor-El and his wife Alura evacuate along with many Kryptonians to Argo City, where Zor-El activates a force field system that separates a chunk containing the city from Krypton, preventing it from being destroyed when the planet's core explodes. Eight years later, Alura gives birth to her and Zor-El's daughter, Kara. Eventually, it is discovered that the separation of Argo City exposed a mineral known as "Kryptonite", which is slowly killing the citizens via radiation. After Alura succumbs to Kryptonite poisoning, Zor-El decides to send Kara and her dog Krypto on a ship headed to Earth. Upon landing, they are greeted by Kara's cousin Kal-El, who is living a double life as Clark Kent and Superman. Kara later tries to adjust to her new life on Earth, while also adopting the moniker "Supergirl".

In the present, Kara travels with Krypto to several planets and parties in celebration of her 23rd birthday. Superman often calls her, concerned that she is constantly off-world and unable to settle on Earth. While stopping at the planet Holzherr, Kara encounters Ruthye Marye Knoll, the last survivor of her family who were murdered by Krem of the Yellow Hills, leader of a ruthless bandit group known as the Brigands. Ruthye requests Kara's assistance in her quest for vengeance, but is denied. Krem hijacks Kara's ship alongside several Brigands, and shoots Krypto with a poisonous dart when he tries to stop them. Upon learning that Krypto has only three days left to live, Kara decides to pursue Krem to retrieve an antidote that he keeps on his person, while also reluctantly taking on Ruthye as her companion.

After a brief skirmish with the Sklarian Raiders, a group of space pirates, Kara interrogates them and learns of Krem's location on the planet Bilquis. There, Kara and Ruthye learn from a local couple, Bomar and Mareck, that the Brigands have been kidnapping young women to force them to be their brides. Mareck attempts to drug Kara to trade her and Ruthye to the Brigands in exchange for their daughter Sarna, but Kara resists and fights the Brigands, and is assisted by the bounty hunter Lobo, who is targeting the Brigands' lieutenant Drom Baxton. Amidst the battle, Kara stops Ruthye from killing Krem, allowing him to escape after killing Bomar and his family. A guilt-ridden Kara decides to pursue Krem alone, and is escorted by several local aliens to the Brigands' location on another planet, Barenton. However, Kara is weakened by the planet's green sun, and is tended to by Ruthye, who secretly followed her.

Ruthye is later kidnapped by the Brigands and taken to their ship, where Lobo is also imprisoned. Ruthye manages to escape her cell and free Lobo, but is caught by Krem as she makes it topside. She is then saved by Kara, who has managed to recover after the planet rotates to a yellow sun and has donned her Supergirl suit. With Lobo's assistance, Supergirl defeats the Brigands and frees the captive women on board. She pleads with Ruthye not to kill Krem, convincing her that it would not ease her pain. As Ruthye walks away, Supergirl picks up her sword and uses it to kill Krem herself. She recovers the antidote and returns to Krypto, saving him in time. Later, as Supergirl bids farewell to Ruthye, she invites her to join her in celebrating the rest of her birthday week.

Some time later, Supergirl reunites with Superman on Earth, where she expresses a desire to stay for the long term, reaffirming that the planet is now her home.