When he was a boy, Owen and his father Kurt were camping in the woods when they stumbled across Storybrooke by accident. The pair are welcomed by Sheriff Graham and go to Granny's Diner where they meet Mayor Regina Mills. Regina, concerned about the presence of outsiders, wants them gone until Owen and Regina bond while they have dinner at Regina's house. Regina changes her mind and wants Owen and Kurt to stay so Owen can be her surrogate son of sorts, and when Kurt wants to leave, Regina forces Graham to prevent them from leaving and arrest Kurt. While Kurt is struggling against Graham, he frantically tells Owen to leave. Regina tries to convince Owen to stay with her but Owen flees, frightened. After finding some policemen, he tries to direct them to Storybrooke, but it is nowhere to be found. Owen, heartbroken, vows to find his father.
Now an adult going by the name of "Greg Mendell", he returns to Storybrooke, only to crash his car into a tree and receive severe wounds. After undergoing surgery at Storybrooke General Hospital, Greg resumes his mission by recording evidence of magic. When Greg's partner Tamara eventually arrives in Storybrooke, together they plan to destroy Storybrooke, as it is the only place on Earth where magic is present. They kidnap Regina and Greg tortures information out of her, before activing the fail-safe trigger in an attempt to wipe Storybrooke out of existence. When that plan fails, Greg and Tamara kidnap Regina's son Henry and escape through a portal to Neverland to meet with the organization that they work for, the mysterious "Home Office".
In Neverland, Greg and Tamara discover that they had been played all along when the "Home Office" turn out to be the Lost Boys. Upon the relevation that they have merely been pawns in Peter Pan's game, Greg refuses to hand Henry over to the Lost Boys, prompting Pan's shadow to descend from the sky and rip his shadow out.
- Greg's alias is a reference to the scientist Gregor Mendel.
- Greg had been a fan of the Star Wars franchise since childhood, even making the opening theme his ringtone.
- S2, E11: "The Outsider"
- S2, E12: "In the Name of the Brother"
- S2, E13: "Tiny"
- S2, E14: "Manhattan"
- S2, E17: "Welcome to Storybrooke"
- S2, E18: "Selfless, Brave and True"
- S2, E19: "Lacey"
- S2, E20: "The Evil Queen"
- S2, E21: "Second Star to the Right..."
- S2, E22: "...And Straight On 'Til Morning"
- S3, E01: "The Heart of the Truest Believer"