Abbie Mills is one of the two main protagonists in the TV show Sleepy Hollow. She is portrayed by Nicole Beharie.
Abbie Mills had a troubled childhood, which included brief run-ins with the law. Both Abbie and her sister, Jenny Mills, dealt with instability at home as children. Their father was an alcoholic and their mother though loving, struggled with what was believed to be mental illness. Abbie and Jenny were very close, often locking themselves in their room to play with their dollhouse and escape their parents. Their father eventually left the family and their mother was declared unfit, leaving Abbie and Jenny to be placed into the foster care system. After an attempted kidnapping of Abbie and Jenny from their foster care home, their mother was institutionalized and later died while she was still in the care of Tarrytown Psychiatric.
Abbie and Jenny then cycled through a few homes before settling in a place that Abbie felt was a good fit. During that time Abbie taught Jenny to pick locks, and they acquired a taste for criminal activity. Around the age of 13, they were sneaking beers in the woods when four white trees and a demon appeared before them. They both blacked out and neither were able to recall much of what happened during the four days they went missing. This was later revealed to be due to Moloch sealing away their memories in Purgatory. After being found by a civilian from a local search party, the girls were taken into police custody and callously interrogated. Jenny insisted on telling the truth about what they had seen even though Abbie warned against it. Fearing that no one would believe her and that she would be removed from her foster home, Abbie lied and didn't back up Jenny's story. Jenny was later put in a mental institution and the sisters remained estranged for nearly 13 years.
Abbie continued to struggle with what she saw in the woods that day and her feelings of resentment and guilt towards her sister. By the time she was sixteen, she was using drugs and pursuing a life of crime. After a botched attempt at robbing a pharmacy, she is taken into custody by Sheriff August Corbin but instead of arresting her he offered her a chance to change. She accepted, and under Corbin's tutelage; took a class in Latin, graduated high school, went to college, rose to the rank of Lieutenant as a police officer and was accepted into an elite FBI entrance program at Quantico to become a criminal profiler. Despite her success, Abbie was still marked by her tumultuous past. She never told Corbin about the demon she saw in the woods or that the experience still haunted her, making her doubt her own perceptions, feel out of place, and struggle in finding purpose. Some of Corbin's last words to her were to ask if her joining the FBI was really about her running away.
Abbie Mills is a lieutenant with the Westchester County Police Department in the small town of Sleepy Hollow. She is poised to leave the town in a week for the FBI Academy in Quantico, Virginia, but with the slaying of her mentor and partner, by a headless horseman, her plans are derailed. Unwilling to divulge the more supernatural elements of partner's murderer without further proof she is forced to team up with Ichabod Crane, an unwilling fugitive from the past who claims to be a soldier in the Revolutionary War and the only person that can corroborate her story. Together they learn they are the Witnesses foretold in the book of Revelation to fight against the coming apocalypse. Throughout the season, Abbie struggles with the death of her mentor, her skepticism, her partnership with Ichabod, rebuilding her relationship with her sister, and accepting her role as a witness.
The arrival of the new Sheriff has Abbie delving deeper into the mysteries surrounding her childhood. Sheriff Reyeshad responded to some the domestic disturbance calls at Abbie's home when she was still very young and was directly responsible for Abbie's mother being placed in Tarrytown Psychiatric. As a peace offering of sorts, Reyes allows Abbie access to her mother's files where she finds out that Lori wasn't mentally ill after all but actually plagued by demons. After confronting a violent haunting at Tarrytown Psychiatric, Abbie and Jenny have a touching moment with the spirit of their mother who reveals that she always knew Abbie was a witness and Grace Dixon had passed down a spellbook that contained clues to a weapon that could destroy Moloch. While pursuing the weapon, Abbie realizes she is one in a long line of women tasked with fighting against the end of days and her legacy gifts her with a renewed sense of self and purpose.
After the defeat of Moloch, Abbie and Ichabod spend time cleaning up the remnants of the demon's evil and repairing a rift in their relationship. Frank Irving's return creates conflicting feelings in Abbie. Eventually it's revealed that her initial hunch is correct and that he is still under Jeremy Crane's control. Jenny pleads with her to try to help Frank and Abbie agrees to look for a way to free him.
She later expresses concern that she and Ichabod seem to be fighting a battle with no goal and Ichabod tells her to simply have faith. They come across an underground library compiled by Thomas Jefferson, and find a sentient hologram of the third US president that tells them that the library was made to provide the Witnesses guidance in their mission. Ultimately, Ichabod and Abbie decide to destroy the Fenestella and the tunnels around it to keep the creatures that guard the area from attacking more people.
Eventually, Katrina joins forces with her son to awaken the magical blood within the residents of Sleepy Hollow using the Grand Grimoire. Understanding the risk evident in such an endeavor, the Witnesses stop them and Abbie kills Jeremy in the confrontation. Katrina goes into the past to correct the mistakes she made so she can raise her son and Abbie follows her to prevent her from killing Ichabod and permanently changing history. Abbie meets her ancestor Grace Dixon and together, they succeed in returning her and Katrina to the future. Katrina attempts to kill her as revenge for the death of her son and Ichabod stabs her to save Abbie, leading to Katrina's death.
After Ichabod leaves Sleepy Hollow, Abbie spends the next nine months speeding through training at Quantico and quickly rising through the ranks at the FBI. She ultimately returns to Sleepy Hollow when she is stationed at the White Plains regional office. After busting Ichabod out of an ICE detention center, she is confronted with the possibility that their mission as witnesses is not truly over in the form of a mysterious Sumerian tablet Ichabod found in his family's crypt.
After witnessing her boss's demise at the hand of demon, Abbie is surprised to find that her old flame from Quantico, Daniel Reynolds, is his new replacement. Ichabod senses that their relationship was more than professional prompting Abbie to warn him to mind his own business. Ichabod concedes in an attempt to be a good roommate but later they both confide in each other secrets that they had been holding onto after a run in with a secret sucking demon. Abbie discloses that a lot of personal stuff had come up in Ichabod's absence and she had ended up finding her father. She had not however worked up the courage to confront him.
Ichabod Crane is Abbie's fellow witness, partner, and very close friend. She met him when he awoke in modern day Sleepy Hollow. Initially, she was inclined to believe he was crazy but when he started to relay accurate details of the Headless Horsemanwho killed her mentor, Sheriff August Corbin, she slowly began to believe his tale. They began to work together to solve the murders of Corbin and Reverend Knapp and eventually learned that they are the beginning of a plan orchestrated by an ancient demon named Moloch to bring about the End of Days. They also learn that she and Crane are the Witnesses spoken of in the Bible and decide to take on the task of preventing the Apocalypse.
Abbie is Crane's sole guide to the 21st century and patiently helps him get acclimated to living in the modern world. She frequently teaches him about new technologies, advances in language, and the new social norms that have arisen in the 230 years since he died. Knowing what a big adjustment it is for him, Abbie does her best to reassure Ichabod that he has home with her in the modern age and though it takes a while Ichabod eventually decides to settle in calling Abbie his greatest boon. They have grown to understand each other intimately and have developed a strong and affectionate friendship.
As Witnesses, however, their relationship is a bit more contentious, with Abbie and Ichabod almost constantly butting heads. Initially, it is Abbie's resistance to believing in her being a Witness that is source of a tension, but morphs into Ichabod having very different ideas as to how to approach the conflict surrounding his family. Later, this comes full circle in Abbie assuming that her role as a Witness is over and trying to move on with her life while Ichabod steadfastly believes their mission is still relevant. Despite this, when they are on the same page, they work very well together. Ichabod always inspires faith and trust in Abbie, even when he doesn't always earn it and Abbie in turn, is always there to remind him he is human and that it is okay to make mistakes.
Abbie is fiercely loyal to Ichabod, it can be argued that he is the single most important person in her life besides Jenny. She's said that her faith in Ichabod is her greatest weakness. Abbie confides in him and is able to sense when something is bothering him. She'll often do small gestures of kindness for him whenever he's feeling down or they've been through a particularly rough time and always tries to get him to see the positives in a situation. She worries over him whenever he decides to take on a task alone and has saved his life more than once. Even when their friendship is tested, Abbie and Ichabod have shown that they are willing to be honest with each other and work through any disagreements or hurt feelings, coming out stronger for it in the end.
Jenny Mills is Abbie’s strong-willed and snarky younger sister. As children the sisters were very close. Sadly, they were both subjected to traumatic childhoods that included a string of foster homes and an encounter with a demon in the woods. Jenny was sent to a mental institution after she insisted on telling the truth about what she saw that day. Abbie escaped a similar fate by lying, but Jenny always believed Abbie’s actions to be a betrayal.
Jenny’s anger at her sister continued to fester over the years, spurred on by a demon named Ancitif that repeatedly took possession of her body. During these fits of possession Jenny would make threats against Abbie’s life. Jenny, fearing she would actually go through with the threats, would often purposefully get arrested in order to keep herself as far away from Abbie as possible. It is later revealed that she was marked that day in the woods, and Moloch had planned to use her to kill Abbie and hasten the coming of the apocalypse.
Jenny was reluctant to forgive her sister even after Abbie apologized, but they do manage a strained working relationship early on. Abbie came to rely on Jenny’s know-how involving just about all things supernatural and the more they interacted the more Jenny visibly softened around her sister. When Abbie found out about the possessions and Jenny’s sacrifice in order to keep her safe, they hugged for the first time in years.