Following McMahon's electrifying series debut, Head Cases, Gardner Camden and his misfit FBI team return. For all fans of Slow Horses and David Baldacci.

FBI Agent Gardner Camden is an analytical genius with an affinity for puzzles. He and his squad of brilliant yet quirky agents make up the Patterns and Recognition (PAR) unit, the FBI's hidden edge, brought in for cases that no one else can solve.

PAR's latest case involves a militia group stockpiling weapons. When their confidential informant in the case is killed, it quickly becomes clear that the militia did not kill him.

As the squad looks into the evidence surrounding his murder, an unidentified man is caught on camera with their informant. This mystery man's picture is connected to another case at the FBI, an unsolved series of murdered women, buried in the ground in north Florida. Could they have uncovered a serial killer? And if so, what is his connection to their C.I.?

As PAR juggles an investigation into both the dead women and the militia, they enroll a new informant, only to find the case escalating in dangerous ways. How will PAR handle a case that increasingly looks like a terrorist plot? And in the serial case, with no puzzles or witnesses, and few leads, how will a group set up to decode riddles be successful?

Praise for Head Cases:

'McMahon's inventive, eventful, smartly written Head Cases, with its brilliant but fallible protagonist, its twisted-minded perpetrator, and its mix of sentiment and intrigue, is a terrific debut that augurs well for further installments in the series' Wall Street Journal

'Everything this crime fiction-lover could want: gripping, twisty, and atmospheric, with a harrowing and intriguing plot, gorgeous prose, and fresh and compelling characters. I want more!' Karen Dionne, author of the #1 international bestseller The Marsh King's Daughter