Sydney is a thirty-four-year-old accountant living in Manhattan. Deeply yearning for a romantic partnership and a family, she actively searches for love online. Despite her intense desire to settle down, she maintains strict safety rules for her dates. She often finds herself disappointed by the reality of the men she meets until a chance encounter changes her outlook.

In the present day, Tom is an attractive, seemingly perfect medical examiner who charms Sydney after a chance encounter. In the parallel past timeline, he is a troubled high school student living in a volatile household. He struggles with violent, intrusive thoughts and harbors a deep fascination with human anatomy and blood.

Gretchen is one of Sydney's close friends in Manhattan, working as a museum curator. She frequently socializes with Sydney and Bonnie, discussing their respective romantic lives over coffee and yoga. She presents a sweet demeanor but occasionally exhibits behavior that Sydney finds difficult to explain.

Daisy is a popular, beautiful high school student in the past timeline. Described by Tom as angelic and perfect, she is the daughter of the local police chief. She assigns Tom duties at a school health fair and occupies nearly all of his romantic thoughts.

Jake is an NYPD detective and Sydney's former boyfriend. Their relationship ended due to his intense dedication to his career over his personal life. He remains highly protective of Sydney, utilizing his professional resources to ensure her safety while pursuing an active murder investigation.

Kevin is a gaunt, unkempt man who looks significantly older than his dating profile pictures. He ignores personal boundaries, displays aggressive entitlement, and refuses to accept rejection after Sydney ends their date. He repeatedly attempts to contact her through various channels.

Slug is Tom's childhood best friend in the past timeline. Known for eating bugs in elementary school and suffering from severe acne, he is socially outcast. Raised by highly neglectful parents, Slug frequently displays anti-social behavior and harbors a cynical view of the world around him.

Bonnie is Sydney's neighbor and friend who also heavily relies on dating apps to find love. She is highly optimistic about a mystery doctor she has been seeing, hoping for a serious commitment. Her sudden, tragic death serves as a major catalyst for the present-day plot.

Randy is the building superintendent who dates Gretchen. He often makes Sydney and Bonnie feel slightly uncomfortable, despite his relationship with their friend. He holds keys to the building's apartments and has a troubled history with previous tenants.

Chief Driscoll is Daisy's father and the local chief of police in the past timeline. He is highly protective of his daughter and spearheads the investigations into the missing high school students in their community. He regularly questions the local teenagers about their activities.

Allison is Daisy's best friend in the past timeline. She intensely dislikes Tom and Slug, actively trying to prevent Daisy from spending time with Tom. She is highly observant and quickly becomes suspicious of Tom's actions, putting herself at odds with him.

Tom's father is an abusive alcoholic in the past timeline. He regularly subjects Tom and his mother to physical and emotional violence, creating an intensely volatile and dangerous home environment that heavily impacts Tom's psychological development.

Tom's mother is a victim of severe domestic abuse in the past timeline. She frequently tries to protect Tom from his father's wrath while simultaneously attempting to keep the family together and cover up the extent of the household's violence.

Brandi is a high school student in the past timeline who goes missing and is later found murdered. She had a known crush on Tom, having received tutoring from him before her disappearance, which casts suspicion on him during the police investigation.