|“||I'll find you, Dad. I promise; I'll never stop looking||„|
|~ Greg's promise|
He is played by Ethan Embry.
In 1983, young Owen Flynn and his father, Kurt, were on a father-son camping trip in the woods of Maine when suddenly a storm overtook their campsite. When they awoke in the morning, a tree had smashed their truck and they decided to hike back to the road to look for help. But instead of finding the interstate, they found a town Storybrooke, that seemed to have appeared out of nowhere. They stayed in town while the local mechanic, Gus, worked on their pickup. At first, the mayor Regina Mills was eager to see them on their way, but as Regina began to realize how empty her life was going to be in Storybrooke with The Curse in-place, she decided to spend more time with Owen and Kurt. Owen and Regina bonded as he told her about losing his mother only 6 months before, and she asked Kurt if he would consider moving to town. He declined, but Regina wouldn’t take “no” for an answer. Using her control of Sheriff Graham’s heart, she ordered Kurt’s arrest. Kurt managed to escape and he and Owen sped for the town line. Graham and Regina pursued in a high-speed chase through Storybrooke, cutting the Flynns off right at the town line. Kurt told his son to run out of town and find his uncle, and Owen reluctantly did so. Regina once more tried to convince young Owen to stay, but he refused. She let him go, but when Owen returned with police officers, the town of Storybrooke was veiled once more by The Curse. Young Owen vowed to find his father one day.
30 years later, after Emma Swan broken The Dark Curse and it became possible for outsiders to find Storybrooke. Mr. Gold and Belle were saying goodbye when the pirate Captain Hook shot her, sending her over the town line and causing her to lose her memories. Gold prepared to retaliate with a magical fireball when suddenly a car came barreling down the road, hitting Hook before spinning out. Emma and David arrived on the scene and got the driver to Storybrooke hospital where Dr. Whale was able to save his life. After the driver woke up, Emma introduced herself and asked about him, his name appeared to be Greg Mendell, and he was a tourist from Pennsylvania. He convinced Emma that he hadn’t seen anything unusual, but when she left, he used his cell phone to call a woman labeled in his phone only as “Her” to tell her she wouldn't believe what he had seen. Greg spent the next few weeks recovering in the hospital. There he would often try to speak with Belle, who had no memory of her previous life and didn't understand that there was magic in Storybrooke. Greg also spied as often as he could, getting footage of Regina using magic on his cell phone. Once he was well enough to leave the hospital, he explored around Storybrooke, making Emma nervous about what he might find. One day, as Greg was walking through the woods, he bumped into Henry, who was off by himself trying to find a way to get rid of magic in Storybrooke. Greg secretly snapped a photo of Henry’s contact information from his backpack and called Regina, saying he was worried about Henry. Later, he followed Regina back to her house where he recorded her ripping out Mary Margaret’s heart and showing it to her. As Greg climbed into his car, a familiar leather braid, given by Kurt Flynn to his son Owen on a camping trip in 1983, dangled from his keychain. Greg once again promised to find his father and it became clear that Greg Mendell is really Owen Flynn all grown up. While Greg continued investigating the town, he ran into Regina, who seemed to remember him from the past. When she finally realized he was Owen, Regina told him that his father left Storybrooke shortly after him. Greg, however, refused to believe her. Later that night, he met with Tamara, his secret lover and partner in crime to bring down Storybrooke. Later he and Tamara capture Captain Hook and made a deal with him, showing him that Mr Gold is alive and that his assassination attempt failed and he made a deal with him order for the pirate to get his revenge. Later, they rescue Hook from an undead Maleficent and capture Regina. Greg tortures her with electric shocks. Regina finally told him that his father was buried at their campsite. He mournfully discovered his father's corpse at the location and reburied him before meeting Tamara again. Together they activated the fail safe that would reverse the curse and destroy the town. However, the plan failed and the two kidnapped Henry and got away in a portal off to Neverland.
As Greg and Tamara arrive in Neverland with Henry, they are met by their employers, Home Office, who are really the Lost Boys, led by Peter Pan's right-hand man, Felix. Greg and Tamara are shocked that they are teenagers. Felix tells them that destroying magic was never really their intention. He then demands that they hand Henry over. Greg and Tamara refused and Felix has the Shadow attack Greg by ripping his shadow from him, killing him.