Riley Abel

Riley Abel is Ellie's best friend and first love, a bold, charismatic teenage girl who leaves the FEDRA military school in Boston to join the Fireflies, the rebel group fighting against the authoritarian quarantine zone government. Her departure devastates Ellie, who felt abandoned by the one person who made the oppressive boarding school life bearable.

Riley returns to find Ellie one night, sneaking her out of the dormitory for an adventure in an abandoned shopping mall. Their night together — exploring a Halloween store, playing arcade games, riding a carousel, and sharing a first kiss on a photo booth strip — is one of the most tender and achingly real depictions of teenage love ever put on screen. It is a night of pure joy in a world that rarely allows any.

The tragedy strikes when they are attacked by an infected hiding in the mall. Both girls are bitten. Riley, knowing what comes next, urges Ellie that they have two options: take the easy way out, or "be all poetic and just lose our minds together." They choose to wait together, but only one of them turns. Riley succumbs to the infection, and Ellie discovers she is immune — a revelation born from the worst night of her life.

Riley's death is the foundational trauma that shapes everything about Ellie. Her survivor's guilt, her willingness to die for a cure, her difficulty trusting people, and her ferocious determination to make her life mean something — all of it traces back to the night she lost Riley. Though she appears in only one episode, Riley is the ghost that haunts the entire series.