Jack Cross is the novel’s protagonist and narrator. She may be physically small—just 5’2”—but she is resilient and strong. Jack maintains her strength and stamina so that she can do her job as a penetration tester, infiltrating clients’ offices to assess their security vulnerabilities. Her job sometimes requires her to scale walls, crawl through ceilings, or outrun security guards, so physical prowess is crucial to her success. Her occupation also requires her to be observant, noting the placement of security cameras, motion sensors, automatic lights, and the like, and Jack has learned to rely heavily on her intuition, which is generally accurate. She is also more tech-savvy than the average person, though not more than her husband, Gabe.

Though she could go by Jackie or something similar, she goes by Jack, providing a clue about her nonconforming and liberated nature. She is not bound by gender expectations; Jack is the more physical partner in her marriage and business. Jack’s choice to keep her maiden name is another way in which she ignores patriarchal social conventions. She says that Arya Stark is her favorite character from Game of Thrones, providing additional indirect characterization and emphasizing Jack’s independence, even if her choices are considered unusual.