The sole survivor of an Army plane crash in the Peruvian hinterlands, Jim Ellison subsisted for nearly two years on his raw animal instincts. When he returned to America and became a police lieutenant, Jim discovered that the abilities that had kept him alive in the jungle now gave him extraordinary senses of perception. With the help of Captain Simon Banks and a grad student Blair Sandburg, Jim now attempts to use these powers to apprehend a terrorist bomber called the Switchman.
In the Peruvian jungle, a Chopec Sentinel named Incacha is enraged by the pollution of his land by a contaminated oil well and the murder of one of his tribesman by an employee of the Cyclops Oil Co. In Cascade, Ellison examines the poison dart that killed the VP of security for the Cyclops Oil Co. and recognizes the markings of the Chopec tribe — the people who helped him develop his Sentinel powers.
Ellison and Sandburg are joined by Megan Connor, a visiting police officer from Australia. When the federal mint is targeted for a major heist, they prepare to apprehend the robbers in the act. It's quickly apparent that Megan has more than a passing interest in the ringleader of this criminal operation. The team knows that the thieves have made their move, when the power goes out in Cascade. In darkness, Ellison is the only one who can see clearly but Megan is dead set on giving the criminals justice.
Jim's friend U.S. Marshall Roger Corman is killed in a car bombing before he can reveal a corrupt marshall that he's uncovered. Only by going undercover can Jim hope to glimpse what is hidden, after the U.S. Marshalls take over the investigation. Jim, Captain Banks, Blair, and Megan Connor, the newest addition to the Sentinel team, conduct their own neighborhood watch.
When Blair's mother Naomi secretly submits her son's Sentinel thesis paper to a publisher, Jim discovers that being famous can be detrimental to your health. While Jim and Blair protect a local union leader Jack Bartley, information from Blair's paper is leaked and Ellison is in the middle of a media frenzy. Unless someone can diffuse the situation, the Sentinel will be forced to leave the city of Cascade -- forever.