Freddie is a 27-year-old Australian writer living in a Boston apartment courtesy of the Sinclair Foundation fellowship. She refers to herself as a "pantser," meaning she writes spontaneously by drawing heavily from her daily life and the people she observes. After hearing a woman scream in the library, she bonds with three strangers and begins using them as the main characters in her latest draft.

Leo is a dedicated fan who serves as a beta reader for Hannah Tigone's latest manuscript. He sends her frequent emails filled with research on Boston locations, weather updates, and suggestions for American phrasing. In Hannah's story-within-a-story, a version of Leo also appears as a fellow writer on fellowship who frequently crosses paths with Freddie.

Cain is a 30-year-old successful author working on his second novel. In contrast to Freddie's spontaneous style, he meticulously plots his books in advance, turning his workspace into a heavily organized incident room. He draws literary inspiration from his difficult youth spent as a runaway in Boston.

Whit is a handsome law student in his early twenties who comes from an elite Boston family. He claims his overbearing parents forced him into legal studies, though he maintains a strong interest in investigative journalism. Freddie nicknames him "Heroic Chin" before the library group officially introduces themselves.

Marigold is a brilliant Harvard University psychology student in her early twenties. She is a former ballerina whose upper body is covered in tattoos, maintaining an edgy aesthetic that distances her from her wealthy background. She quickly forms intense attachments to her new friends.

Hannah is a successful Australian author currently writing a new mystery novel set in the United States. Grounded in Australia by strict pandemic lockdowns and catastrophic bushfires, she relies heavily on digital correspondence to accurately capture the Boston setting for her book.

Boo is an unhoused Boston man who struggles with prescription drug addiction. He crossed paths with Cain years earlier when Cain lived on the streets as a teenager. He holds strong personal convictions about justice and retribution.

Mrs. Weinbaum is an older, retired woman who lives in the apartment below Freddie. She frequently monitors the activities of her neighbors and eagerly inserts herself into their affairs under the pretense of offering help.

Jean is Whit's mother and a highly successful, polished defense attorney in Boston. She presents a cool, unemotional exterior and utilizes her considerable resources to monitor the people surrounding her family.

Caroline is an ambitious investigative journalist for a Boston tabloid called *The Rag*. As a member of the elite Brahmin social class, she often leverages her family connections to advance her career, though her sudden death drives the central mystery of the story.

Isaac was an older, unhoused man who lived on the streets of Boston. He took a teenage Cain under his wing, teaching him how to survive before eventually becoming the victim of an unsolved murder.

Lauren is a reporter working for *The Rag*, the same tabloid that employed Caroline Palfrey. She works diligently to uncover local crime stories and harbors strong opinions about her late coworker's professional conduct.

Darryl manages a Boston soup kitchen frequented by the city's unhoused population. He is familiar with many of the local regulars and provides a safe space for people seeking warm meals.

Michael is an FBI agent investigating a string of unsolved cases in the Boston area. He intervenes in Hannah's digital life to warn her about the potential dangers of communicating with unknown readers.

Peter is Hannah Tigone's lawyer. He steps in to formally negotiate the parameters of her interactions with fans and authorities, ensuring she assumes no legal liability for external events.

Geraldine is Freddie's late sister. Her childhood death profoundly impacted Freddie's family dynamics and served as the emotional foundation for Freddie's first successful piece of writing.