Primal Fear is a 1993 American thriller novel by William Diehl about Aaron Stampler, an altar boy accused of murder, and Martin Vail, the attorney defending him.

[1] It was adapted into the 1996 film of the same name, starring Richard Gere and Edward Norton.

[2] The characters of Stampler and Vail appear in two additional novels by author Diehl, Show of Evil and Reign in Hell.

[3] Martin Vail, a lawyer of "bad-boy" fame, is defending Aaron Stampler, who is seen standing with a bloody knife when the Archbishop of Chicago was murdered.

Knowing he would lose, Vail used his unorthodox skills to take legal advantage.