Marie Quinn's husband, a concert violinist who is not involved in the Unknown Organization but plays a crucial role in preserving Marie's legacy and supporting her mission.

The novel's central antagonist, an abstract and evolving threat that embodies fear and cynicism, challenging the protagonists’ efforts to understand and counter its influence.

A curious and intelligent member of the Antimemetics Division who demonstrates the significance of instinctive knowledge in confronting and overcoming unknown threats.

A former mentor to Marie Quinn and founder of the Antimemetics Division, who becomes involved in the conflict as both a source of critical knowledge and a minor antagonist.