The Greek god of travelers, language, and thieves. Intrigued by human nature and their awareness of death, he accepts a wager to grant human intelligence to fifteen dogs at a veterinary clinic. He views mortals with a mix of amusement and genuine affection, occasionally meddling in their lives to test his theories.

The Greek god of poetry, music, healing, and plague. He initiates the wager, believing that human intelligence is an occasionally useful plague that will only bring misery to the dogs. Unlike his brother, he views mortals primarily as subjects for observation rather than beings worthy of deep sympathy, and he actively interferes to ensure he wins the bet.

A black poodle who values freedom above all else. After gaining human intelligence, he leads the breakout from the clinic but hesitates to fully commit to the newly formed dog pack. He feels more comfortable around humans than his fellow dogs and struggles with the existential burden of his new consciousness, attempting to balance his canine instincts with complex thought.

A large Neapolitan mastiff who takes command of the dogs who flee to the park. He finds the empathy born from his new self-consciousness unbearable, especially when hunting prey. To combat this internal turmoil, he institutes strict rules aimed at forcing the pack to return to traditional dog behaviors and brutally suppresses any human traits.

A mutt who wholeheartedly embraces his new human intelligence, particularly the abstract nature of language. Instead of returning to his dog instincts, he begins composing and reciting poetry. His linguistic skills confuse and anger the rest of the pack, forcing him to survive his new reality mostly in exile while holding onto memories of his first human master.

A pragmatic beagle who accepts that his size prevents him from leading the pack. Unburdened by the philosophical dilemmas that plague Majnoun and Atticus, he uses his human intelligence purely as a tool for survival and self-advancement. He readily performs tricks and manipulates both humans and dogs to secure food, safety, and shelter.

The father of the Greek gods and the ultimate dispenser of justice. He oversees the natural order of the world and takes a strict view on his sons' meddling with mortal creatures. He demands respect from mortals and immortals alike, valuing hierarchy and proper sacrifice over frivolous wagers.

A human woman living in Toronto who nurses Majnoun back to health. She develops a profound, complex method of communication with him, treating him as an equal rather than a pet. She attempts to understand Majnoun's thoughts on abstract concepts like love and equality, though their differing species perspectives sometimes create friction.

Nira's husband, who approaches Majnoun with a highly traditional view of the human-dog dynamic. He doubts that Majnoun possesses genuine intelligence, believing the dog is simply highly trainable. His commanding presence causes Majnoun to instinctively view him as the leader of their household.

A small dog in the newly formed pack. The gift of human intelligence allows her to form a surprisingly deep and emotionally complex friendship with Bella, experiencing a level of companionship impossible in her previous life of pure instinct.

A large dog who joins the High Park pack after the clinic breakout. She forms a uniquely profound emotional bond with Athena, utilizing her new consciousness to experience friendship well beyond basic canine instinct.

One of the larger dogs in the pack who aligns closely with Atticus. He works actively to suppress his own self-consciousness, using his intelligence only to serve his basic dog instincts and violently enforce Atticus's strict rules.

A member of the pack who fully supports Atticus's vision of returning to traditional dog behaviors. He serves as violent muscle for the pack leader, actively working to root out and punish dogs who embrace their new language.

A member of the High Park pack who tries to ignore his human intelligence to better fit in. However, he frequently clashes with the artificial hierarchy Atticus attempts to impose, testing the limits of the new pack structure.

A female dog in the pack who accepts her newfound self-consciousness but longs for the simplicity of her past. She uses her intelligence to reflect on her previous life, expressing regret over losing track of the puppies she previously birthed.

A small dog who struggles under the rigid and increasingly violent hierarchy of Atticus's pack. He grows weary of constantly performing submissive roles to appease the larger dogs and bonds with Benjy as they look for ways to escape their circumstances.

A dog in the newly formed pack who firmly refuses to conform to Atticus's demand that they abandon human language and thought. She decides she would rather accept exile than return to mindless instinct.

One of the dogs at the veterinary clinic who receives human intelligence. She reflects on her severe physical pain and her memories of her mistress, consciously choosing to stay in her cage rather than flee with the other dogs.

A dog who gains human intelligence and chooses to return to his original human owners rather than join the park pack. His new self-consciousness causes him to recognize his humans' condescending behavior, leaving him profoundly disillusioned.

A dog who returns to her human owners after the clinic breakout. Her heightened awareness makes her deeply sensitive to her owners' ongoing neglect, which severely impacts her mental state and causes her to withdraw completely.

Prince's original human master from his time in Alberta. He encouraged Prince's playful nature during their time together. Prince carries a deep, lasting emotional attachment to Kim long after they are accidentally separated in the bustling city.

A human woman who briefly takes Prince in and later provides shelter and food for Benjy. She initially views Benjy as highly intelligent because he performs tricks, but she entirely misinterprets his actual thoughts and motivations.

Clare's partner. Benjy attempts to analyze him strictly using canine hierarchy rules, observing his private interactions with Clare to determine who holds the top position in their household, which leads to massive miscalculations.

One of the Greek Fates, responsible for cutting the threads of mortal lives when their time is up. She strictly adheres to the rules of the universe and becomes intensely frustrated when divine interference makes her job impossible to perform correctly.