Margins
Head Cases book cover
Head Cases
2025
First Published
4.00
Average Rating
181
Number of Pages

Head Cases follows an enigmatic group of FBI agents as they hunt down a murderer seeking his own justice in this electrifying—and commercial—series debut. Gardner Camden is a walking analytical brain with an affinity for riddles, puzzles, and codes. It makes him the perfect fit for the Patterns and Recognition (PAR) unit of the FBI, a team of five brilliant but misfit agents tasked with solving cold cases. Gardner's smart, but he's all business--except for his seven-year-old daughter and occasional visits to his elderly mother, he prioritizes his work and justice over everything else, no matter the cost. With rumors of PAR about to be disbanded, the team can’t afford to make any mistakes. A serial killer from one of Gardner’s solved cases, presumed to be dead for over a decade, is found murdered, and then soon after, another body with a similar story. The mastermind murderer has left clues and riddles for Gardner and his team--a mathematician, a sniper and weapons expert, a computer analytics specialist, and their leader, a career agent--as they track him across the country. With the threat of PAR dissolving, Gardner must work to solve the riddles before it’s too late. McMahon’s suspenseful and irresistible thriller confronts the scales of justices in the face of a twisted vengeance plot as this engaging cast of characters works together to stop a misguided vigilante.

Avg Rating
4.00
Number of Ratings
14,103
5 STARS
27%
4 STARS
50%
3 STARS
20%
2 STARS
3%
1 STARS
1%
goodreads

Author

John McMahon
John McMahon
Author · 5 books

John McMahon is the author of THE GOOD DETECTIVE and THE EVIL MEN DO, both featuring Georgia detective P.T. Marsh. The New York Times Book Review called McMahon “one of those rare writers who seems to have sprung out of nowhere” and whose debut novel is “pretty much perfect.” In his role as an ad agency creative director, he has won a Gold Clio for his work on Fiat, and he’s written a Super Bowl spot for Alfa Romeo. He currently lives in Southern California with his family and two rescue animals.

548 Market St PMB 65688, San Francisco California 94104-5401 USA
© 2026 Paratext Inc. All rights reserved