Wizards Beyond Waverly Place finale reveals Billie is Alex's daughter

In the two-part season finale of Wizards Beyond Waverly Place, which was released on Disney on Oct. 8, Alex Russo, played by Selena Gomez, appears to sacrifice herself to stop a rift linking the human world to a realm of dark magic. The episode resolves a season-long mystery by revealing that Alex is the mother of Billie Russo, and ends with Alex and the antagonist falling through the portal as it closes, leaving her fate unresolved.

The revelation that Billie is Alex's daughter comes after a tense confrontation with the villain Lord Morsus, who has been manipulating Billie to open the portal. A tear falling onto a locket found earlier in the episode restores a suppressed memory: a young Billie being left at a wizard boarding school while Alex and Justin wipe their memories of her to protect her from a powerful adversary. The memory also identifies Lord Morsus as Damian Penwolf, Billie's paternal grandfather, and explains why Billie's family history had been erased.

The finale ties together several plot threads from the season. Billie had grown close to a character named Quentin, who is revealed to be an orc recruited by Morsus. Morsus uses shapeshifting to infiltrate Alex's...