Lark is an indie musician who secretly operates as a serial killer, targeting men who prey on women and children. She struggles with intense claustrophobia and unprocessed trauma from her adolescence, leading her to hide her violent inclinations from her family and even her closest friends. Beneath her cheerful and accommodating exterior, she is fiercely protective of those she loves, a trait that pushes her into an unexpected marriage of convenience with a man she initially despises.

Lachlan is a skilled assassin and "cleaner" who desperately wishes to retire from his violent profession. His true passion lies in his work as a leather artisan, a stark departure from the grim reality of his daily obligations under a cruel boss. Protective and observant, he is burdened by guilt over a past mistake involving Lark and enters an arranged marriage to protect his brothers from organized crime retaliation.

Abe is a highly religious and deeply disturbed man carrying a profound grudge against those he holds responsible for a personal tragedy. Driven by the belief that he hears divine whispers guiding his actions, he is determined to exact revenge for the death of his brother, Harvey. His fixation makes him a lingering and dangerous presence on the periphery of the main characters' lives.

Ethel is Lark's formidable great-aunt, a woman whose physical deterioration from a terminal illness masks a sharp, ruthless, and highly strategic mind. Though her family often underestimates her due to her declining health, she orchestrates complex situations from behind the scenes. She is entirely dedicated to Lark's happiness and safety, proving to be a pragmatic and unflinching ally.

Sloane is Lark's best friend and an established serial killer known as the "Orb Weaver," specifically targeting other killers. Despite her own dark inclinations, she remains a steadfast and loving presence in Lark's life. She shares a deep bond with her husband, Rowan, and functions as part of the emotional core that Lark fights desperately to protect.

Rowan is Lachlan's younger brother and a serial killer known as the "Boston Butcher." He is deeply in love with his wife, Sloane, and maintains a tight bond with his siblings. Rowan's past actions in eliminating another killer place a target on his back, inadvertently catalyzing the dangerous circumstances that force Lachlan and Lark into their arrangement.

Fionn is the brother of Lachlan and Rowan, working as a doctor who frequently tends to his older brothers' various physical injuries. He carries emotional baggage from a past heartbreak, which complicates his current romantic prospects. He maintains a close relationship with his brothers while struggling to verbally commit to the woman who currently loves him.

Rose is a dedicated circus performer with the Silveria Circus and a good friend to Lark. She harbors deep feelings for Fionn Kane, though their relationship is marked by tension due to his reluctance to openly admit his affections. She is supportive of Lark's happiness and proves willing to step into physically dangerous situations for the people she cares about.

Leander is a cruel and domineering figure who runs a criminal enterprise focused on torture and "cleaning" services. He relies heavily on Lachlan's skills and actively blocks him from retiring, holding a past mistake over his head as leverage. Leander is entirely comfortable with extreme violence and demands absolute obedience from his subordinates.

Damian is Lark's stepfather and the head of a powerful organized crime family. He maintains strict control over his operations and reacts ruthlessly to threats against his business or his family. While he is deeply entrenched in the criminal underworld, he cares for Lark and is highly protective of his associates.

Nina is Lark's mother and an active participant in the Covaci family's organized crime operations. She is deeply suspicious of the Kane brothers when her business associates begin turning up dead. Like her husband, she approaches threats with cold pragmatism and a willingness to eliminate potential risks to her family and empire.

Dr. Louis Campbell is the former headmaster of Ashborne Collegiate Institute, the school Lark attended. He is a corrupt administrator who actively condoned and covered up the sexual abuse perpetrated by one of his teachers. His past actions make him a prime target for Lark's brand of vigilante justice.

Ava is Lark's sister, a relatively grounded presence in the Montague-Covaci family dynamic. She is frequently present for family gatherings and is notably stunned by Lark's sudden and uncharacteristic decisions regarding her personal life.

Conor is an associate of Lachlan's who works on Leander's "cleanup crew." He assists Lachlan in various illicit tasks, ranging from retrieving vehicles at murder scenes to executing kidnappings and providing intelligence on rivals.

Bob Foster is a business rival of Aunt Ethel and a primary suspect in the string of murders targeting Covaci associates. He operates a busy club that Lark and Lachlan infiltrate to gather financial evidence regarding the hits on their family.

Claire is Fionn Kane's ex-girlfriend, whose past rejection broke Fionn's heart and nearly caused him to relocate. Her lingering presence and overly familiar interactions occasionally cause misunderstandings among the Kane siblings' social circle.

Mr. Vernon is a former teacher at Ashborne Collegiate Institute who sexually abused a teenage Lark. Though already deceased by the events of the novel, his monstrous actions are the catalyst for Lark's severe trauma and her subsequent transformation into a killer of predatory men.