(CENTERS FOR DISEASE CONTROL AND PREVENTION VIA ASSOCIATED PRESS)

A young man’s body was found in a warehouse. He had been stabbed to death. The authorities wanted to track down the killer. But here’s the twist: They weren’t homicide detectives. They were epidemiologists.

It’s a true story from Monrovia, Liberia, in 2015, when the country faced a deadly Ebola outbreak. And it’s the subject of a recent episode of the NPR podcast “Hidden Brain,” which explores why people make the choices they do.

Host Shankar Vedantam explains that the episode was prompted by a call from Tom Frieden, the director of the U.S. Centers for Disease Control and Prevention. Frieden wondered why the podcast hadn’t tackled public health topics, and he suggested this case, which involved two CDC employees.

Their job was to help find everyone who had had recent contact with this young man, whose corpse tested positive for Ebola. The victim had been part of a 35-member street gang whose members had turned on him in a knife fight. Blood flying in close quarters meant they were all at risk of contracting the Ebola virus — as were their families, friends and other connections.

Tracing contacts is complex in almost any circumstance, but the process is even tougher when the people you’re seeking are hiding from the police.

But the CDC workers enlisted a local epidemiologist and started searching slums and drug dens.

Incredibly, they managed to get almost the entire gang to go into an isolation facility. The trick was not to use any trickery. Instead, the Liberian government promised support for their families and even provided cocaine to the addicted members of the gang so that they wouldn’t go into withdrawal while in quarantine.

But they still needed to find the person who held the victim down during the fight. His name? Time Bomb.

A big break came when they met someone claiming to be Time Bomb’s younger brother. He was with a woman and a baby. At that point, Vedantam says, the epidemiologists did something “very kind and very wise”: They offered the woman money to help feed her child.

The young man’s demeanor changed. He revealed that he was actually Time Bomb, and he agreed to cooperate by staying in touch and going into quarantine if he developed symptoms, which he did not.

It’s not exactly a happy ending: One person died of Ebola contracted from the stabbing victim. But it’s a fascinating way of learning that one of the most important tools for stopping an outbreak is trust.