Deadly Animals

Deadly Animals is English author Marie Tierney’s debut crime novel, published in 2024. The book follows 14-year-old Ava Bonney after she finds the corpse of her missing classmate. Ava’s macabre interests in decomposition and criminology assist her and Detective Seth Delahaye as the case turns to serial murder at the hands of Nathaniel Marlowe, who thinks he is a wolf. Deadly Animals explores themes including The Fine Line Between Fascination and Obsession, The Psychological Impact of Conformity, and Free Will and Moral Responsibility in Violent Crime. Marie Tierney was a finalist for the Daily Mail’s First Novel competition.

This guide follows the Henry Holt and Company 2024 hardcover edition.

Content Warning: The source material and guide feature depictions of bullying, mental illness, child abuse, child death, death by suicide, animal death, and graphic violence.

Plot Summary

Deadly Animals opens with 14-year-old Ava Bonney sneaking out of her apartment to visit her secret roadkill body farm, where she studies the decaying bodies of animals. During her late-night examination, Ava stumbles upon the corpse of her missing classmate, Mickey Grant, and she anonymously reports the body to the police. Detective Seth Delahaye begins his investigation with his partner Detective Steve Lines by going door-to-door. Ava feels emboldened to share her knowledge of similar historical crimes with the men, and the detectives are impressed. Investigators learn that the killer attacked Mickey like a dog, leaving bite marks all over his body. Delahaye and Lines interview their main suspects: Bob Aster, a registered sex offender, and Pete Ancona, a surly ice cream man. Local teens alert the detectives to a strange animal prowling about, and the detectives find a jumble of human and animal footprints near the crime scene.

Ava continues to conceal her discovery of the body. She gets attacked by a bully at school, but a handsome older boy, Nathaniel Marlowe, saves her. Ava grows suspicious of her mom’s boyfriend, Trevor, who sneaks out of the house at odd hours. Throughout the investigation, Ava calls in her theories to the police with a disguised voice, and Delahaye nicknames the mysterious caller Miss Misty. Delahaye and Lines ask Ava for help identifying local teen hangouts, and Ava leads them to Mickey’s secret den at Banlock Farm, where they discover the kill site as well as a chilling garden of animal bones. The detectives interview the land’s owner, Neville Coleman, but the man’s Alzheimer’s syndrome makes him forgetful.

Another boy, Bryan Shelton, goes missing from his home. Delahaye finds a hidden candy mouse in the boy’s room and believes the abductor used it to lure Bryan. The community grows frustrated at the lack of action, and a group of kids vandalize Bob Aster’s house, believing he is the culprit. Ava’s friend John has a strange interaction with Nathaniel when he helps the boy move a dead dog off the street, and another teen, Paul, hears Nathaniel making dog-like vocalizations. Maureen, Neville Coleman’s caregiver, sees a mysterious creature prowling around the hospital.

Ava stumbles on Bryan’s body, and she preserves evidence on his hand before having John report the corpse. When police investigate the scene, Delahaye sees that the killer’s ferocity has progressed, as this time they left a dead dog with the boy. Ava and John start their own investigation into the murders. Ava theorizes that the killer suffers from clinical lycanthropy, making him believe he can transform into a wolf. Ava suspects the creature seen around town is the killer in a wolf suit. When Ava calls the theory in, Delahaye recognizes her voice.

A third boy goes missing and is found dead, and the police find evidence that the same killer is responsible. Delahaye investigates a sweets shop and re-interviews suspects—one of whom, Bob Aster, has disappeared—but he continues to run into dead ends. Delahaye suspects that Neville Coleman holds the key to the case, and he researches the man’s history as a dog breeder. After his family died, Coleman raised a secret grandson in neglectful conditions before the boy was forcibly removed into foster care. Delahaye finally meets with an expert on clinical lycanthropy to expand the killer’s profile.

Meanwhile, Ava continues her investigation by using her dog Fizz as a ruse to talk with Neville Coleman. Ava learns that her family has ties to the Colemans, and Mr. Coleman’s sharp recollection of the past makes Ava suspect he is faking his dementia. Ava visits Banlock Farm again and finds the hidden graves of Coleman’s family, as well as fresh flowers left by a recent visitor. Ava also visits Nathaniel’s Sky Den on the roof of an apartment building. Police capture an elusive graffitist who left messages around town taunting the police, but it is only a scared local boy.

The killer’s next victim, Keith Magaw, escapes from captivity but is hit by a car while fleeing and falls into a coma. His notebooks describe the underground lair where he was held. Delahaye and Lines investigate Neville Coleman’s other property, where they find the killer’s trophies and a recent campsite. Ava and John realize that Nathaniel Marlowe is the killer and long-lost grandson of Neville Coleman. Delahaye learns the same information from Keith when he wakes from his coma. Delahaye learns that Nathaniel suffered a brain injury a year prior that gave the boy an uncontrollable temper.

John finds Nathaniel’s underground lair and sees Nathaniel, dressed in his homemade wolf suit, attack a young boy in the open. Ava follows a hunch and finds Nathaniel at his Sky Den. The boy has completely given in to his canine alter-ego. John and Paul have secretly followed Ava, and they fight Nathaniel. Delahaye intervenes, but Nathaniel takes Ava as a hostage. Ava stabs Nathaniel with a pencil, and he jumps off the roof.

After Nathaniel’s death, Delahaye learns that Nathaniel’s father knew about his son’s condition and tried to contain him in a cellar, but Nathaniel eventually overpowered him. Nathaniel left his father to die at Banlock Farm, but the man survived and slipped into a coma. Neville Coleman confesses that Nathaniel was raised by his dogs, and their violent separation likely created permanent trauma. Delahaye gifts Ava Nathaniel’s x-rays and drawings, which show that the boy was happiest in the company of dogs. Ava decides to change her study from decomposition to criminology so she can study how monsters like Nathaniel are made.