This is Hidden Brain. I'm Shankar Vedantam.

It's a summer evening in northern Indiana.

Three teenagers are in their car headed to a church-sponsored volleyball game.

It's 1978.

The three Ulrich girls, sisters Judy and Lynn and their cousin Donna,

drive down US 33 in a Ford Pinto.

Judy is behind the wheel. She's 18, a recent high school graduate. Two years older than her little sister, Lynn.

Donna is also 18. Around 6.30, Judy slows down. She's worried she might have left the cap to the gas tank on the trunk.

She puts on her hazard lights.

A few seconds behind the Pinto on the same road, Roger Duggar is driving a Chevy van. He's looking for a cigarette

pack on the floor. When he looks up, the slowing pinto is right in front of him. He's going about

50 miles per hour, and he doesn't have time to stop.

At first, Roger doesn't think the crash is that bad.

Then, he smells gasoline.

Later, reporters will recount testimony from a third driver who saw what happened. There was a puff of flame about 12 to 18 inches long at the rear of the car.

Almost immediately, the Pinto explodes into flames.

The eyewitness gets out of his car with a fire extinguisher and runs over to see if he can help.

By the time the first state trooper arrives, the pinto is scorched.

Inside the car, Lynn and Donna are dead.

Judy is outside, alive, but badly injured.

She's taken to a burned unit at a nearby hospital.

She lives for about nine more hours.

...