Cormoran is a private investigator and former British Army military policeman who lost part of his leg in an explosion in Afghanistan. He works from a cramped flat above his Denmark Street office. Burdened by memories of warfare and his chaotic childhood, he relies on a gruff exterior to handle emotionally taxing situations. He prioritizes catching a dangerous killer over accepting lucrative but mundane cases.

Robin is Strike's assistant and aspiring investigative partner. Raised in a stable Yorkshire family, she possesses a long-standing ambition to work in criminal investigation. She left her university psychology program following a traumatic assault. She now views her work with Strike as a chance to reclaim her life and help other vulnerable women.

Donald is a former private in the King's Own Royal Border Regiment and a prime suspect in the severed leg case. He previously served a sixteen-year prison sentence after Strike arrested him for severely abusing his wife. He suffers from a form of arthritis. He possesses a volatile temper that he masks beneath a layer of superficial charm.

Jeff is a would-be musician and the former stepfather of Cormoran Strike. He possesses a dark intensity and an obsession with celebrity, the occult, and Charles Manson. He was acquitted of causing his wife Leda's fatal overdose years ago, though Strike remains certain of his guilt.

Matthew is an accountant and Robin's long-term fiancé. He values social status, financial security, and conventional success above all else. He strongly disapproves of Robin's investigative career, viewing it as poorly paid and excessively dangerous.

Noel is a Gulf War veteran who works a series of transient security jobs. He sustained a traumatic brain injury that ended his military career. He blames Strike for this injury and holds a deep grudge, while continually targeting young girls in domestic settings.

Eric is a Detective Inspector with the Metropolitan Police. He maintains an amicable working relationship with Strike, unlike many of his colleagues. He initially focuses his investigation on a known gangster, relying on standard police procedures that sometimes conflict with Strike's private inquiries.

Leda was a well-known music fan who lived a chaotic lifestyle in various London squats and communes. She died of a heroin overdose years before the events of the story. She possessed a generous but naive nature, frequently bringing unsuitable men into her children's lives.

Shanker is a heavily tattooed man with a scarred face who operates within London's criminal underworld. He first met Strike as a teenager when Leda took him in after a gang fight. He remains intensely loyal to Strike's family and assists the detective by tracking down hard-to-find individuals.

Elin is a beautiful former violinist and current classical music radio presenter. She lives in a luxurious Regent's Park apartment and is currently divorcing her wealthy husband. Her affluent lifestyle creates a sharp difference from Strike's gritty daily realities.

Kelsey is a sixteen-year-old girl who lives with her half-sister. She exhibits signs of body integrity identity disorder, expressing a strong desire to amputate a healthy limb. She fixates on Strike due to his public status as an amputee.

Hazel is Kelsey's older half-sister and guardian. She experiences immense grief and frustration regarding her sister's psychological struggles and habitual lies. She firmly defends her partner from police suspicion regarding Kelsey's activities.

Carver is a Chief Investigating Officer who harbors a deep professional grudge against Strike from a previous case. He actively dislikes the private investigator and refuses to collaborate, preferring to follow his own instincts and suspect lists.

Stephanie is a young woman living with Jeff Whittaker above a fish and chip shop. She works as a sex worker and gives her earnings to Whittaker, who repays her with physical abuse and control.

Sarah is an old university friend of Matthew. She frequently provokes Robin by expressing open admiration for Strike's hero status and physical appeal, masking deeper tensions within her history with Matthew.

Charlotte is Strike's ex-fiancée from a toxic sixteen-year relationship that ended abruptly. She is beautiful and emotionally volatile. She quickly married another man specifically to spite Strike, leaving him financially destitute.

Brittany is the stepdaughter of Noel Brockbank. She confided in a friend about her stepfather's abuse but later retracted her testimony after facing intense pressure and threats from Brockbank.

Holly is Noel Brockbank's sister. She has a history of enduring abuse from male family members, including her brother, whom she eventually forced out of her home under threat of exposure.

Rhona is the ex-wife of Donald Laing. She suffered horrific torture at his hands when she attempted to leave him, sustaining injuries that left her permanently unable to have children.

Margaret is Rhona's mother. She holds deep gratitude toward Strike for rescuing her daughter years ago and freely shares information about Laing's current status and past behavior.

Alyssa is Noel Brockbank's girlfriend who works at a strip club. She lives in Bow with her two young daughters and initially believes Brockbank's claims that his ex-wife fabricated allegations against him.

Terrence is a notorious gangster whom Strike previously testified against in court. He has a reputation for sending severed body parts to his enemies, making him an obvious target for initial police suspicion.

Lorraine is a former girlfriend of Donald Laing. She lived with him until he disappeared with her money and jewelry, though she mistakenly insists he was never violent.

Ilsa is Strike's best childhood friend. She frequently hopes for a romance between Strike and Robin, expressing disappointment over Robin's upcoming wedding to Matthew.

Graham is a former Special Investigative Branch colleague of Strike. He works in an Edinburgh office and provides Strike with essential military files regarding former suspects Laing and Brockbank.

Linda is Robin's mother. She visits from Yorkshire and offers her daughter unconditional support, promising to back Robin whether she decides to proceed with her wedding or cancel it.

Jason is a young man active on a body integrity identity disorder forum. He wishes to meet Strike, falsely believing the private detective is a voluntary amputee rather than an injured veteran.