A is a sixteen-year-old disembodied spirit who wakes up in the body of a different person each day. A has no control over the gender, race, location, or appearance of each body they occupy, but they do always wake up in the body of a person their age. Comfortable living as both male and female, A is non-binary and does not exclusively identify with either gender. When A wakes up in a new body, they have access to that person’s memories, which helps them navigate the day. Over the years, A has learned that it is impossible to prevent the switch to a new body at midnight each night. Even if A stays awake, A’s spirit involuntarily—and painfully—rips from the body it is inhabiting in order to move on to the next. A has accepted this existence, choosing to fall asleep before the switch each night, so that it occurs peacefully. Additionally, since A never wakes up in the same body twice, A tries to maintain a healthy detachment from each person’s life.
When A wakes up in the body of a high school student named Justin, everything about A’s existence changes. The day begins normally, with A heading to school and attending Justin’s classes. Soon, however, A meets Justin’s girlfriend, Rhiannon. Through observing Rhiannon’s behavior and accessing Justin’s memories, A learns that Justin treats Rhiannon poorly, often making her feel small, anxious, and insecure. Although A usually attempts to maintain a careful distance from the friends and loved ones of the hosts, A feels an inexplicable desire to get to know Rhiannon better. When A impulsively suggests they ditch school together, Rhiannon agrees and suggests they go to the beach.
During their day together, A and Rhiannon converse deeply and form a strong emotional connection. A’s loving and attentive behavior surprises Rhiannon, as she believes A to be the more typically disengaged Justin, but she is thrilled to see her “boyfriend” making more of an effort to connect. Over the course of the day, A begins to fall in love with Rhiannon, making the 24-hour limit on their time together ever more devastating. When A returns back home at the end of the day, the fragile illusion of their happy time with Rhiannon dissipates. Knowing that Justin will regain his body the next day and resume treating Rhiannon poorly, A calls Rhiannon to remind her that every day cannot be like the one they just shared. This change in tone disappoints Rhiannon, but she says she understands. A ends the day wishing it was possible to stay in Justin’s body.
Over the next several days, A tries to devise ways to see Rhiannon again. When A wakes up in the body of a girl named Amy Tan who lives an hour away from Rhiannon, A immediately drives to Rhiannon’s town. Pretending to be scoping out the school ahead of a family move, A approaches and befriends Rhiannon. Rhiannon is kind and welcoming, offering to show A around for the day. This encounter causes A’s feelings for Rhiannon to deepen and grow. On another day, when A wakes up in the body of a strait-laced rule follower named Nathan Daldry, A decides to crash a party in Rhiannon’s town to see her. A pretends to be the party host’s cousin, a story that Rhiannon easily believes. At the party, A and Rhiannon converse, dance, and become fast friends. Before leaving, A gives Rhiannon a fake email account for Nathan in order to begin a correspondence with her. The night leaves A exhilarated and happy, but this quickly devolves into anxiety as A rushes to make it home in time for the switch at midnight. Running out of time, A pulls over to the side of the road and quickly goes to sleep. A feels guilty that Nathan will wake up the next day with no idea where he is and no recollection of the night, but A feels it was worth it for the chance to see Rhiannon.
A and Rhiannon begin to correspond via email, with Rhiannon still believing that A is Nathan. Unfortunately, the real Nathan also begins to send emails to A’s other email account, which A accidentally left open on Nathan’s computer. Believing that he has suffered a demonic possession, Nathan begins to send threatening messages to A, demanding an explanation. A evades Nathan’s questions and dodges his emails, hoping that Nathan will eventually give up and return to his normal life.
Rhiannon finds out that the host from the previous weekend’s party does not have a cousin, so she emails A to ask for an explanation. A finally resolves to tell Rhiannon the truth, asking her to meet at Clover Bookstore. When Rhiannon arrives, she is shocked to see A occupying the body of a girl named Megan Powell. At first, Rhiannon does not believe A’s story, but as A reveals more details from the day they shared at the beach, Rhiannon begins to see the truth. When A confesses love for Rhiannon, she becomes overwhelmed and asks to part ways for the day.
A and Rhiannon continue to correspond via email, and A visits Rhiannon whenever a car is available. Seeing A occupy each new body, Rhiannon begins to get used to A’s unique existence, looking past the unusual circumstances to see the person within. Rhiannon begins to reciprocate A’s romantic feelings, but she still has reservations about all the obstacles that accompany this unconventional relationship.
At the same time, Nathan grows more and more desperate for answers, relentlessly harassing A via email. Nathan also involves a religious leader named Reverend Poole to lend validity to his claims of demon possession. Reverend Poole and Nathan begin to speak to news outlets, spreading Nathan’s story and urging others to come forward if they believe they have experienced a possession, too. The increasing publicity of the story begins to worry A, but A continues to evade Nathan’s questions, only offering vague denials of being a demon.
As A and Rhiannon’s relationship progresses, their problems increase, too. Rhiannon comes up with a plan to spend the weekend at her uncle’s cabin, and A happily agrees. Rhiannon and A enjoy their first day together, but A must leave before midnight to get the host's body back home before the switch. Promising to return the next day, A leaves Rhiannon waiting at the cabin. Unfortunately, A is unable to keep this promise, due to a host's family issues the next day. This causes a major fight between A and Rhiannon. A few days later, A wakes up in the body of an overweight boy. Although A and Rhiannon try to go on a date and enjoy each other’s company, Rhiannon becomes upset because she cannot look past the host body’s appearance to see A within. The relationship grows increasingly tense, and Rhiannon eventually breaks up with A. Rhiannon affirms that she deeply loves A, but she believes the obstacles to their relationship to be insurmountable. A is heartbroken but agrees to remain friends.
Feeling despondent over Rhiannon, A turns to the one other person who is aware of A’s existence, finally deciding to tell Nathan Daldry the truth. A arranges to meet up with Nathan at a Mexican restaurant. Although Nathan is surprised to see A in an unfamiliar form, he believes A’s story immediately. Nathan expresses gratitude for the explanation, and A leaves the meeting believing it went well. When Nathan asks to see A again the next day to witness the switch for himself, A tentatively agrees.
The next day, A visits Nathan’s house. Immediately, A notices that Nathan is acting strangely. When Nathan leaves to get A glass of water, he returns with Reverend Poole. Nathan then leaves A and Reverend Poole alone to converse. At first, A sees Reverend Poole as the religious zealot the media has portrayed him to be, but Reverend Poole makes a shocking revelation. There are more people just like A—and some of them know how to stay in other people’s bodies for much longer than one day. The person standing in front of A is not Reverend Poole at all, but rather another disembodied spirit, who has been possessing Reverend Poole's body for an undisclosed amount of time.
The person occupying Reverend Poole’s body tells A that there are many spirits like them. This revelation is incredibly shocking for A, who has always felt alone in the world. The spirit occupying the Reverend also claims to be able to teach A to stay in host bodies for longer periods of time. Even though A initially feels intrigued, the spirit’s obvious darkness and menacing energy give A pause. Conflicted, A runs away. A few days later, A wakes up as a girl named Zara. Zara has a perfect life, the kind of life A would do anything to stay in for more than one day. Overcome with temptation to change the inconsistent circumstances of their existence, A reaches out to Reverend Poole for more information about his previous claims.
During this time, A's relationship with Rhiannon is distant and tense, until the day A wakes up as Alexander Lin. Immediately, A takes a liking to Alexander, who is creative, kind, and personable. This gives A an idea, and A subsequently contacts Rhiannon, asking to spend the day with her. Although Rhiannon is still hesitant about a romantic relationship with A, she agrees to pretend that they are on a first date. A and Rhiannon enjoy their day together, culminating in a home-cooked dinner in Alexander’s treehouse. In the treehouse, A tells Rhiannon everything about Reverend Poole and his claims. Earlier that day, however, when A asked for more information, Reverend Poole’s cold, calculating disregard for the lives of hosts provided A with clarity. After realizing that Reverend Poole is evil, and that it is morally wrong to possess hosts for more than one day, A decided to run away from Maryland and end things with Rhiannon. When A woke up in Alexander Lin’s body, A felt that he would be someone Rhiannon could eventually love. So, A planned to connect Alexander and Rhiannon with the feigned "first date," finally letting the hope of a relationship with Rhiannon go. Rhiannon is devastated to lose A, but she eventually understands. Before the end of the night, A and Rhiannon promise to remember each other forever.
The next day, A runs away, viewing this action as a new beginning.
