One reason for the hostility, no doubt, was that the people-smuggling business in Nimruz was suffering. Until recently, Zaranj profited immensely from the tens of thousands of Afghans, displaced by war and poverty, who emigrate west each year. The border is only a 10-minute drive from downtown, where more than 150 hotels, owned by local smugglers, once catered exclusively to a steady flow of migrants crossing the open desert into Iran. In those days, you could walk up to a checkpoint, pay a bribe and get into a car, Tehran-bound. The highly efficient system was administered by the Baluchis: a small ethnic minority who remained united through a distinct language and culture long after their homeland was divided among three often-rivalrous nations. Indeed, the Baluchis from each of those nations had become adept at working together to ferry from one country to another, and sometimes to another, humans, goods, drugs, fuel, weapons and — especially since the recent collapse of the Iranian rial — currency.

A few years ago, Iran designated the province that borders Nimruz a “no go” area for foreign residents and shortly thereafter began erecting a 15-foot-high concrete wall that now runs more than half the length of its 147-mile border with Nimruz. The Iranian border police — manning guard towers, each within sight of the next — were also said to have changed. There came increasing reports of Afghans being shot and killed by the same authorities who once benignly waved them through. While most of these stories are unverified, they nevertheless reinforced a growing sense that the old road to a new life was now closed. Today migrants who come to Nimruz must travel another 10 hours south into Pakistan, then cross from there into Iran. The journey consists of three legs. Afghan-Baluchi smugglers take you part of the way; Pakistani-Baluchi smugglers take you a littler farther; Iranian-Baluchi smugglers finish the job. For the first stretch — a narrow dirt road through uninhabitable, lunar flatland — roughly 300 drivers share a rotating schedule, each working one day a month. These were the men preparing to depart from Ganj, bristling at my questions about the bomb.

Before I left, I followed a group of young Hazaras down an alley to another lot where still more trucks were being loaded with people. As I rounded the corner a man cried out: “Watch this guy! Get away from him! Watch out!” It was the second time in less than a week I was mistaken for a suicide attacker — a uniquely unpleasant sensation that I had not experienced anywhere else in Afghanistan. The misunderstanding arose from a combination of two factors, I think: the extreme paucity of foreigners who had ever been to the city and the extreme degree, even by Afghan standards, of paranoia and suspicion that pervaded it. Residents of Zaranj spoke obliquely and in low tones, always on the lookout for passers-by, forgoing words whenever meaningful grins or nods sufficed. At times, the aura of mistrust felt histrionic, and it was often tough to tell when the furtive whispers or emphatic pleas for anonymity were necessary and when they were affected. You had the sense everyone fancied himself an operator; you also knew that some of them probably were. The second person I met in Nimruz — a commander with the National Directorate of Security, Afghanistan’s intelligence service — told me a few hours after I arrived: “There is one person here whom you absolutely cannot trust. He is in the pocket of Iran. You must be very careful with this man and do whatever you can to avoid him.” The man the commander named was a senior official in the provincial government and the only other person I had met there so far.

Iran looms just as large over western Afghanistan as Pakistan does over the east — and nowhere is this more keenly felt than in Zaranj, where the land beyond the wall can represent anything from benevolent neighbor to malicious oppressor. But while Pakistan’s machinations in Afghanistan often feel obvious, Iran’s have proved far harder to discern. Everyone I spoke to in Nimruz, for example — provincial officials, smugglers, police, border guards — insisted that “Iranian agents” had placed or arranged for the placement of the land mine that killed the two Baluchi drivers and injured Gulbadeen. As for why, each source offered a different theory — usually in a hushed voice, after glancing to the left and right.

If nerves were especially raw when I visited Zaranj, it was because two weeks earlier an extraordinary spectacle of violence seemed to justify even the most paranoid anxieties. On Aug. 13, a few days before Eid al-Fitr, which marks the end of the Muslim holy month of Ramadan, the police were on heightened alert after receiving intelligence that an attack against government targets might be imminent. When a white Toyota Corolla station wagon approached the checkpoint on its way into the city, the officers on duty motioned for it to stop. A bearded man in the passenger seat produced a handgun and shot at them. The station wagon accelerated toward the city center, and the officers gave chase. After several rounds shattered the station wagon’s rear window, its driver lost control and smashed into a wall. When the driver and the passenger stumbled out and tried to run away, the officers opened fire, killing them both.