- “I'm done reading about heroes. I want to be one.”
- ―Henry to David
Henry Daniel Mills is one of the main characters of Once Upon a Time. Henry is the biological son of protagonist Emma Swan, and the adopted son of former antagonist Regina Mills. A lonely boy, Henry came to believe that the people living in his small town were under the effect of a powerful curse that robbed them of their memories of their past identities as fairytale characters. This led him to look up his birth mother, whom he knew to be the key to everyone's salvation.
During the first Curse
Henry is born in a prison in Phoenix, Arizona, and given up for adoption by his birth mother, Emma Swan, because she wanted to give him his best chance in life. His biological father, Neal Cassidy, was never told as Emma found out unexpectedly in jail she was pregnant. He is found by Mr. Gold and adopted by the mayor of Storybrooke, Maine, Regina Mills.
In Storybrooke 2001, when Mayor Regina Mills begins to feel the emptiness in her position of power of controlling the town, she believes the only way to fill that void is to adopt a child, but she realizes that she'll have to wait a long time due to the possibility of being placed on a waiting list, so she turns to Mr. Gold for help, but he then cautions her that when she becomes a parent, she should consider that she will be putting a child first. Days later, Regina learns that a baby has become available for adoption, so she travels to Boston to take custody of the child. The only warning the agency offers Regina is that the family has opted for a complete blackout concerning their lives (the sealed documents that Emma signed). Regina, convinced that she only needs the future, takes the newborn infant in her arms and names him after her father, Henry.
An older Henry receives his cherished book of fairy tales from his teacher Mary Margaret Blanchard, discovering that the residents of Storybrooke are characters from it after noticing he is the only one in town who ages. His realization of Regina's true identity strains his relationship with her, and she sends him to regular therapy sessions with Dr. Archie Hopper to end his belief in the curse. Hoping to break the curse, Henry finds his biological mother Emma Swan in Boston and brings her to Storybrooke.
He eventually convinces her of the truth by consuming a sleeping curse intended for her by Regina, nearly resulting in him dying. However, he is awoken with true love's kiss by Emma, which also breaks the curse.
After The First Curse
After the breaking of the Curse, Henry reunites with Mary Margaret, David, the Dwarves, Ruby and Granny, While Emma and her parents hug, he calls David, "Grandpa", which David joyfully acknowledges before embracing him as well. He is terrified when he hears that Dr. Whale is leading a mob to Regina's house, and begs Emma and the others to stop it; because Regina is still his mom. After Emma saves Regina's life so she would not break her promise to Henry, she asks her if it is true Henry asked Emma to keep her alive; apparently wondering if Henry loves her after all.
Emma and Mary Margaret are then dragged into a portal, leaving David (Prince Charming) to look after him.When Emma and Mary Margaret vanish into the Hat, Henry comes in with Ruby to stop Regina from strangling David. He calls her an evil queen when he hears what happened to his mom and grandmother, and tells her he does not want to see her until they come back. Then he goes to live with David in Mary Margaret's apartment
Following the death of Regina's mother Cora, and her vowing to avenge Mary Margaret, Henry seeks to remove magic from Storybrooke. When Emma and Regina stop the trigger enacted by Greg Mendell and Tamara from destroying the town, he is kidnapped by the pair and taken to Never Land, where it is revealed that Peter Pan (Henry's great-grandfather) wants possession of him as he owns "the heart of the truest believer". Pan eventually persuades Henry to give him his heart, putting it into Pan's body, telling him it will save magic. Regina reclaims the heart and resurrects Henry. However, Pan inhabits Henry's body in Storybrooke, until Gold corrects the bodies. However, Pan enacts the original curse again, forcing Emma and Henry to leave Storybrooke forever.
Before the Second Curse
Directly after driving out of Storybrooke, Henry and Emma obtain false memories of their life together. Henry's past is altered and instead of being put up for adoption, he lives with Emma in New York City. They recall a fire breaking out in Emma's apartment in Boston, which causes them to start afresh in New York.
During Second Curse
A year later, Henry and Emma are having breakfast in their New York apartment. She goes to answer the door, but does not recognize the man who claims to know her. After Emma shuts the door in the stranger's face, Henry asks about who was at the door, but she apparently doesn't know him.
Over the course of eight months, Emma dates a man named Walsh, who Henry takes a liking to. One night, Emma is proposed to by Walsh, though she is hesitant to say yes. Henry urges Emma to accept, since Walsh has proven himself to be a kind and loving man, and won't leave her like his biological father did. In the morning, Henry sends a text to Walsh asking him to come over for dinner at eight o'clock. Later, Emma realizes that he is right and the past is keeping her from looking forward, which Henry humorously takes to mean she is going to marry Walsh. Henry mentions the pre-scheduled date she and Walsh will be having and has already decided to sleep over at a friend's house so they can have privacy. The following day, he learns Emma did not accept Walsh's marriage proposal. As Henry begins prepping to head off to school, Emma suggests that they take time off and go on a trip. A guest arrives at the apartment, who Henry recognizes as the same man that came to their door as well as the person Emma had arrested for assaulting her. She introduces him to Henry as Killian, a client from work. Shortly after, the three travel via car to the town of Storybrooke.
A year later, Hook restores Emma's memories, leading her to return to Storybrooke with both Henry and Hook to save their family. With no memories, Henry is initially confused and suspicious of Emma's decision to relocate to Storybrooke, until Emma restores his memories with his book.
After the Second Curse
Henry later helps Regina to search for his storybook's writer. When Emma's magic goes out of control, after being manipulated by the Snow Queen, Henry tries to help calm her down, only to end up getting injured. He joins Mary Margret, David, Regina, and the others in their hunt for Emma. After the search is over, he watched Emma's display in the sky, when the Snow Queen decides to enact the Spell of Shattered Sight. Later on, Regina seals Henry in her office, to prevent other people from hurting him when the spell engulfs Storybrooke. Henry, after the spell, shows Emma and Regina a room full of empty books in the same house that Gold and Belle had their honeymoon at.
Henry discovers a page in the book which is different to the others and then discovers a key. He realizes that The Author of the book is trapped within that page, and so he and his family decide to free him, however he escapes and allies himself with Mr. Gold.
Once The Author has found his ink, he begins to write a new book, entitled "Heroes and Villains". Henry manages to locate the Author and they both eventually find themselves trapped within it.
Henry finds out that a happy ending for a hero in this universe will return things to the reality that he knows, but Isaac leaves him to be attacked by a ogre. However, Henry is rescued by the "Ogre Slayer": Rumplestiltskin, a heroic knight. Using Isaac's book as a guideline, Henry seeks out Regina, who is living life as a bandit "Snow White" in this universe. He tries to convince her that he is her son, but Regina does not believe him and throws the book into a fire. Convinced that a true's love kiss between Regina and Robin could solve the problem, he suggests that she seek him out, although Regina already knows him as a fellow thief who is a major rival of her's.
Regina informs Henry about the marriage of Robin Hood and Zelena, which he realizes will mark the permanence of the alternate universe when the church bells ring. Regina, still not believing him about him being her adoptive son, then suggests that he try finding his other mother, if he truly believes that the "Heroes & Villains" tale is real. When Henry mentions that his other mother was known as "the Savior," Regina tells him of the legend of "the Savior," who was trapped in a tower in the middle of the ocean by the Evil Queen. Henry goes to the Jolly Roger to recruit Hook and finds that the pirate is now employed by Captain Blackbeard. With this reformed Hook lacking in bravery, Henry has to take care of Blackbeard himself before telling Hook that he must help him rescue his mother, Emma, from the tower. Henry and Hook sail towards the tower where Emma is locked away and proceed to knockout the dark guard on duty. When Henry reaches Emma at the top, he is surprised to find that she was able to keep her memories as part of a cruel curse.
Henry and Emma return to Regina's cave, where the three of them go to Robin's wedding, but Rumple suddenly appears to stop them. Emma and Henry try to distract Rumple as Regina tries to work up the nerve to interrupt the ceremony. Rumple aims his sword at Henry, but Regina jumps in front of him just in time to take on the hit herself, opting to save Henry instead of pursuing Robin. Henry then picks up Isaac's quill and it activates, meaning that he has been appointed as the new author. Using the blood of the "light savior," Regina's, Henry writes, "because of Regina’s sacrifice, Isaac’s villainous work was undone."
Everyone is transported back to Storybrooke and the Sorcerer's Apprentice tells Henry more about his new powers as the Author, which do not include the ability to resurrect the dead, such as Neal, since he died in the real world. He urges Henry to resist the temptation of embellishing stories with the quill and Henry responds by snapping it in half, saying that "no one should have that much power."
- There is some inconsistencies on the show as to where Henry was born. While some episodes mention he was born while Emma was in prison, other episodes have shown him born in a hospital before Emma gives him up.