Forget that Daniel Silva’s novels are popular thrillers, two of which made the New York Times’ best-seller list. Forget that the screaming-orange jacket flap to his current novel, The Marching Season, ends with overheated prose that touts his book as “[f]illed with breathtaking plot twists [that spiral] to a riveting conclusion.” No, Silva, 38, is a seasoned journalist who covered the Middle East for United Press International; not for him the easy potboiler drawn straight from the brain. He goes out and gets the story first.

For The Marching Season, Silva, who lives in Georgetown, went to Northern Ireland (“for many days,” he remembers, rather vaguely) to study the terrain and the people. Nominally, his book follows the deadly dance between fictional CIA officers, American ambassadors, and international assassins. But when Silva went to Ulster, he made a point of hanging out with the ordinary folk. Except, it should be noted, the notion of “ordinary” in Northern Ireland—where Protestants and Catholics have been at each other’s throats for generations—has an entirely different meaning.

“You cannot go into a bar in Northern Ireland as an outsider and not be recognized as one immediately,” he says. “That’s how each community protects itself from the other. You can’t walk into a bar in West Belfast without looking into a video camera and stepping into a steel-caged door. The monitors are above the bar, and the people drinking look up to see who you are and say, ‘Yeah’ or ‘No’ to let you in or not.”

When Silva found himself admitted, he would sidle up and explain that he was an American visitor, and did they mind if he joined them for a pint? He was coy, initially at least, about his novelistic intentions. “When you joined them at the table, they’d be picking at you: ‘Who are you?’ Everyone is very suspicious. ‘Are you wearing a wire?’ ‘Are you an agent?’ Once you got through all that, it was OK, but people were still very guarded.”

In Belfast, Silva says, you can’t really walk around the way you would in a normal place: “You don’t cross between a Protestant and a Catholic neighborhood—lots of people have gotten killed that way.”

One day Silva took a camera into West Belfast to take a few pictures to help out his memory, but he found himself afraid to reach into his bag to pull it out. “I was walking behind a group of British soldiers, and suddenly one of them spun around and aimed his weapon at me,” he said. “I was looking down the barrel of that gun. Later, I was telling a fellow about this, and he said, ‘I live with that every single day when I walk down this road.’ It was utterly fascinating, but also the saddest thing I’ve ever seen.”—Louis Jacobson