Michael Tighe of the Psychotechnic Institute has been kidnapped by Thomas Bancroft, a politician with ties to an authoritarian movement called the Actionists. Tighe's adopted son, Simon Delgatty, sets out to find him, but is himself captured by Bancroft and taken to his base on an island off the coast of Mexico. In the course of raising Delgatty, Tighe has trained him to exert conscious control over what are normally subconscious and autonomic brain functions. This allows Delgatty to speed up or slow down his metabolism at will, and also allows him to tell what other people are thinking by listening to them subvocalize their thoughts.