Dean Harbinger Harrow is the cheerful, avuncular head of the McMasters Conservatory for the Applied Arts. He firmly believes in the school's ethics, notably the "Four Enquiries" that justify murder as a necessary act of compassion for the innocent. He provides witty, philosophical aphorisms to his students to normalize their deadly education.

Cliff is an aircraft engineer at Woltan Industries who enrolls at McMasters under the sponsorship of an anonymous benefactor after a botched murder attempt. Educated at MIT and Caltech, he possesses a logical mind and a deep sense of compassion for those harmed by his cruel boss. He seeks to eliminate this executive to prevent dangerous airplane malfunctions and avenge his friends.

Gemma is an English hospital employee who arrives at McMasters to learn how to deal with an extortionist coworker. Unlike other students, she struggles to adapt her strong personal morality to the school's teachings and refuses to treat murder lightly. She maintains her genuine nature, declining to use disguises or manipulate others casually.

Known as Doria Maye in Hollywood, she adopts the name Dulcie Mown while attending McMasters. She is a famous actress seeking to eliminate a vindictive studio head who threatens to ruin her career. Her acting experience makes her a natural at assuming false identities, utilizing disguises, and manipulating targets.

Merrill Fiedler is a ruthless executive at Woltan Industries who prioritizes cost-cutting over airplane safety. He uses his power to extort employees into sexual favors and systematically destroys the careers of anyone who opposes his methods. His immense vanity makes him blind to the resentment he causes.

Adele is an administrative executive at St. Ann's Hospital in England. She steals credit for Gemma's work and actively blackmails her to prevent Gemma from applying for a promotion she wants for herself. She wields her knowledge of Gemma's past as a weapon to secure her own advancement.

Leonid is a powerful and vindictive Hollywood studio head. When actresses reject his advances, he uses his position to systematically destroy their careers by forcing them into humiliating roles. He maintains a private beach house where he expects starlets to entertain him.

Jud is a problematic McMasters student who physically resembles a creepy clown. He frequently disregards the school's rule against harming innocent bystanders and quickly develops a bitter rivalry with Cliff. His impulsive behavior causes constant concern among the faculty.

Jack is a propulsion engineer at Woltan Industries who acts as a surrogate uncle to Cliff. He loses his job and his reputation after attempting to address safety concerns regarding the new W-10 airplane. His subsequent death serves as the final catalyst for Cliff's murderous plans.

Liliana is Jack Horvath's widow. She serves as a maternal figure for Cliff, offering him a sense of replacement family as she grieves the sudden loss of her husband. She deeply resents the lack of respect shown by her husband's former employer.

Erma is the Assistant Dean and Chief Financial Officer of McMasters. She frequently clashes with Dean Harrow over educational philosophy, preferring a specialized, profitable approach over his broad, holistic curriculum. She views the school primarily as a business enterprise.

Captain Dobson is a former police officer who works for McMasters. He intercepts failed murderers before traditional law enforcement can arrest them, offering them the choice between prison or enrollment at the school. He also teaches classes on creating alibis.

Sergeant Stedge is Dobson's partner and a McMasters employee. He assists in the capture and blindfolded transportation of new students to the hidden campus. He operates vehicles and handles the physical logistics of bringing recruits into the fold.

Cubby is a bumbling McMasters student who uses an ice cream truck as part of his deletion practice. He frequently struggles with his coursework and fears he will be failed and deleted by the faculty.

Simeon is an arrogant McMasters student who physically resembles an "evil British prince." He attempts to boost his own grades by tricking other students into fake deletion scenarios.

Vesta is the campus nurse and the instructor of the mandatory "Eroticide" class. She teaches students how to use seduction as a weapon and attempts to coach Gemma out of her impractical ideas about befriending extortionists.

Cora is the inventory supervisor at Woltan Industries. Her suicide, brought on by Fiedler's sexual extortion and the circulation of illicit photographs, serves as a major catalyst for Cliff's decision to commit murder.

Eddie is an executive at AirCorp, the main competitor to Woltan Industries. Though cutthroat in business, he draws a hard line against endangering human lives or facilitating murder, opting not to exploit deadly flaws in rival aircraft.

Wes is the head of security for AirCorp and a former comrade of Eddie's from the Korean War. He harbors secret romantic feelings for his boss and remains fiercely protective of his physical and professional safety.

Finny is a security guard at the Hollywood studio where Doria works. He supplements his income by spying on the actors and selling information about their private lives to the vindictive studio head.

Father Pugh acts as a priest and faculty member at McMasters. He holds dispensations from multiple churches and views the lethal work of the school as doing God's work, attempting to guide struggling students through their moral dilemmas.

Monsieur Tissier is the head chef at McMasters. He teaches students about poisons and toxins while they work kitchen duty to earn pocket money, turning culinary preparation into lethal education.