A FEW HOURS characteristically behind schedule, Amtrak's Southwest Chief rolls into Albuquerque, New Mexico, at the small station that it shares with the Greyhound bus service on the edge of downtown.

Most people step off to stretch their legs or have a cigarette during the layover, the longest smoke break in the entire trip. That's when two plainclothes agents come aboard the train on a rainy day in March 2019.

One agent walks to the back of the aisle in the first coach car and waits, quietly observing. The other is tasked with getting people to talk and open their bags. His name is Jarrell, or Jay, Perry, and he's done it hundreds of times before.

Today, he seems confident that he will find someone on board carrying drugs — or at least a substantial amount of money. He flashes a smile and a badge. A young, disheveled man in a seat by the entrance to the car agrees to let Perry search his three bags. The agent flips through the man's luggage with tactical speed