When a headless body washed up in the calm waters of the Texas gulf coast, investigators began to unravel a crime that led first to a drug cartel assassin, then to a locked safe containing​ more than a kilo of cocaine, methamphetamine, a gold-plated pistol— and U.S. Border Patrol agent Joel Luna’s badge.

At a moment when Border Patrol may relax its hiring standards to meet President Trump's executive order for 5,000 new agents, The Atlantic traveled to south Texas to explore a dark corner of the nation's largest police force. There, investigators discovered that the victim was killed in a tire shop owned by Joel Luna’s two brothers, and that the agent used drug money to buy homes for them. “Whether he did it out of greed or out of love for his family, only he knows,” said Gustavo Garza, the prosecutor who brought murder charges against Luna.

Though the brutality of the crime is uncommon on the U.S. side of the border, corruption in the Border Patrol is widespread enough to “pose a national security threat,” according to the Department of Homeland Security. More than 140 agents have been arrested, charged, or convicted in the last dozen years. Joel Luna "is not one bad apple," said James Tomsheck, a former senior official at Customs and Border Protection, "he's part of a rate of corruption that exceeded that of any other U.S. federal law enforcement agency." This documentary explores Luna's case and its implications for the Border Patrol's new hiring spree. For more, read the story ‘Not One Bad Apple.’