September 11, 2001. Almost everything seemed to go as the terrorists intended. Almost. Flight 93—which crashed not on the Capitol or the White House, but in a Pennsylvania field—was one terrorist shy of the other flights. The brave Americans who rose up that day against the hijackers were aided by a man they never met and whose story has never been written. His name is Jose Melendez-Perez. This book tells his story.

As Michael Smerconish recounts in riveting detail in Instinct, more than a month earlier a young Saudi national had arrived at Orlando International Airport on a flight from London. He didn’t speak English, and his customs paperwork was blank except for his name: Mohamed al-Kahtani. He had a one-way ticket. Soon, INS agent Melendez-Perez was called to the scene. To others, al-Kahtani seemed like a befuddled tourist eager to see Disney World. At risk to his job for the appearance of racial profiling, Melendez-Perez—drawing on his training and his instinct—sent al-Kahtani packing back to Dubai.

Melendez-Perez changed history that day. But he is not alone. In addition to telling his story and that of al-Kahtani—who was later captured in Afghanistan and sent to Guantanamo Bay—Instinct examines the quick thinking of other Americans who faced fanatics; for example, the Washington State border inspector whose gut told her something wasn’t right about the would-be millennium bomber. Michael Smerconish provides fascinating insight into the post-9/11 world of interrogation. And he poses tough questions about how the CIA and Homeland Security can protect America in a post–9/11 world. Most pointedly: Have we learned from the example of Jose Melendez-Perez?