Nemo is the captain of the Nautilus, and while he is away on a sea voyage, his family is killed by several unknown assailants. Swearing revenge, he eventually tracks down and kills each person involved in his family's deaths, and he murders at least one of them with a harpoon. He comes to regret his actions after realizing how empty his life had become because of only living for vengeance, and later saves a young boy, Liam, who became orphaned after someone killed his father. Liam wants revenge on his father's killer, but Nemo convinces him to let it go, as he does not wish for Liam to go down the same path as him. As Liam stays with him, Nemo eventually develops a close father and son relationship with him. ("Dark Waters")
After the Evil Queen enacts the Dark Curse, time freezes in many places, but Nemo takes Liam outside the curse's bounds, allowing the boy to age and eventually become his first mate on the Nautilus.
During a search for a key that will open a portal to a land known to Nemo as the Mysterious Island, Nemo's harpoon, the same one he used to kill one of his family's murderers, somehow becomes enchanted and allows him to track down Hook. Nemo passes himself off as a crewman on Hook's ship, where he purposely stalls the vessel in order to kidnap him aboard the Nautilus. Knowing about Hook's quest to kill the Dark One for taking away his family, he openly suggests that what Hook needs is a family, not revenge. Hook joins Nemo and Liam on a treasure hunt, in which he is almost dragged away by a Kraken, only for the captain and first mate to save him. After finding a chest with a key to the Mysterious Island, Nemo invites Hook to come with him to this new world, with the promise that he will never have to lose family again. Instead, Hook sees a familiar looking knife, the same one he used to kill his father, and that it belongs to Liam, who is revealed to be his half-brother. When Liam finds out the truth, Nemo encourages him to be stronger than he was by not seeking revenge. Liam refuses and then tries to stab Hook, but Nemo takes the hit instead. As Liam holds a dying Nemo, Hook escapes off the ship. Nemo luckily survives, but only by reaching the Mysterious Island, where his story becomes paused. ("Dark Waters")
By Mr. Hyde's will, Nemo is taken from the Land of Untold Stories to Storybrooke, where his story becomes unpaused, causing the stab wound he had before to reform. While he is close to death in the woods, David discovers him and sends him to the hospital for surgery. Liam, believing Nemo died after arriving in Storybrooke, attempts to kill Hook in retaliation. Hook knocks him out, and while Liam is recovering in the hospital, he and Hook make peace. Meanwhile, Nemo's surgery goes well and he is wheeled into the room, where he reunites with Liam. ("Dark Waters")
After making a full recovery from his injuries, Nemo decides to resume travelling the seas with Liam and his other crewmen on the Nautilus. He says goodbye to Hook at the docks and praises him for taking his advice about giving up revenge in favor of making a family. Hook confesses to Nemo about his past catching up with him because of something he did that has hurt the family of the woman he loves, Emma, yet he cannot bring himself to be honest with her about it. Nemo tells him that guilt is as bad for the soul as revenge is, and that keeping the secret to himself will eat him up. He advises Hook to either be truthful with Emma or simply forgive himself without telling anyone about the secret. Hook is unsure if he can do either, however, Nemo suggests that, no matter what, he has to make a choice in the end. As the Nautilus crewmen are moving supplies onto the submarine, Nemo is approached by Hook, who asks to join him on his sea voyage, in order to find himself again and be the man that Emma needs him to be. One night the Nautilus is set to leave, Hook goes below deck to tell Nemo that he's changed his mind and wants to work things out with Emma. Nemo gives his blessing to Hook, which Hook echoes in return, but suddenly, an alarm goes off indicating the submarine is submerging underwater. Gideon reveals himself as the culprit and briefly apologizes to Nemo for messing with the Nautilus, however, he simply can't have Hook in Storybrooke with what he has planned for Emma. ("Page 23")
- The casting call describes him as "the hardened leader of the Nautilus submarine, who's a zealous believer in a cause that takes him from 20,000 leagues under the sea to the destiny that he won't let anyone prevent him from achieving".
- One of the Authors' Books contains a black and white version of an illustration from an 1871 edition of Twenty Thousand Leagues Under the Sea, illustrated by the French painter Alphonse de Neuville and the French painter and illustrator Édouard Riou. It shows Captain Nemo taking observations of the deck of the Nautilus. ("Only You")
- The epaulettes on Nemo's shoulders are the same design worn by Gerhart and Alphonse Frankenstein in "In the Name of the Brother", the Duke of Weselton in "The Snow Queen", and the Royal Palace Guards of Oz in "Heart of Gold" and "Our Decay". ("Dark Waters", "Page 23", "A Wondrous Place")
|Once Upon a Time: Season Six|
|"The Savior":||"A Bitter Draught":||"The Other Shoe":||"Strange Case":||"Street Rats":||"Dark Waters":||"Heartless":||"I'll Be Your Mirror":||"Changelings":||"Wish You Were Here":||"Tougher Than the Rest":|
|"Murder Most Foul":||"Ill-Boding Patterns":||"Page 23":||"A Wondrous Place":||"Mother's Little Helper":||"Awake":||"Where Bluebirds Fly":||"The Black Fairy":||"The Song in Your Heart":||"The Final Battle Part 1":||"The Final Battle Part 2":|