Full story
In Los Angeles, six teens who were childhood friends have drifted apart since the death of Nico's sister, Amy. Alex Wilder gets everyone together at his house: Nico Minoru, Karolina Dean, Gert Yorkes, Chase Stein and Molly Hernandez. That night they spy on their parents' meeting and watch a ritual in which a young woman named Destiny is killed. The parents are the Pride, a powerful group that has spent years handing over victims in exchange for favors from a mysterious figure named Jonah.
Season 1 is the investigation. Each kid finds a gift: Karolina glows in colors, Molly has absurd strength, Nico wields a magic staff, Chase builds combat gauntlets and Gert controls an actual dinosaur, Old Lace. They learn Amy was also a victim of the scheme and that Jonah wants to dig up something huge under the city. In the final showdown with their parents the truth comes out, and the six run away, framed for Destiny's murder.
In Season 2 they hide in an abandoned mansion, the Hostel, while the Pride and the police hunt them. Jonah turns out to be an alien and Karolina's biological father. He wants to free a ship buried beneath Los Angeles. Some of the parents turn on him after learning Jonah killed Amy. Nico takes Jonah down with her staff, but the win doesn't last: Victor, Stacey and Tina end up controlled by Jonah's alien family, and Leslie is pregnant with his child.
The third and final season brings in Morgan le Fay, a sorceress trapped in the Dark Dimension who wants to merge that world with Earth. She draws Nico in and corrupts Robert Minoru. There's a crossover with Tandy and Tyrone from Cloak & Dagger, who help the group on a mission into the Dark Dimension. The war is costly: some Pride parents die, and Gert is fatally wounded fighting Morgan's witches and dies in Chase's arms.
The ending plays with time. The Runaways find a way to go back and undo Gert's death, and Morgan is beaten. But Alex finds a note from his future self telling him to hide "Mancha" and to kill Nico. The series closes with the whole group alive and together after three seasons of running from their own parents. It never got a follow-up, so you're left feeling these six still had plenty of story left.