December 1991, four teenage girls, an Austin yogurt shop.

By the time firefighters put out the flames, three bodies were burned beyond recognition.

The evidence was destroyed.

Two innocent men went to prison, and the real killer was dead before anyone knew his name.

This is the story of how science finally caught up to the truth.

The So here's what happened on December 6, 1991 in North Austin.

Four teenage girls were working and hanging out at a place called,

I can't believe it's yogurt. Two of them, Eliza Thomas and Jennifer Harbison, were employees.

Jennifer's younger sister Sarah and her best friend, Amy Ayers, had stopped by to catch a ride

home. These were normal kids doing normal kid things on a Friday night.

Someone came in through the back door right before closing time.

What happened next was so violent, so methodical, that it would haunt investigators for more than three decades.

The girls were bound with their own underwear. They were gagged.

Each one was shot in the head. Amy Ayers,

who was only 13, was shot twice. Then the killer set the building on fire. When the firefighters

arrived, the yogurt shop was engulfed in flames. They poured thousands of gallons of water onto the

scene, which saved the building, but destroyed almost

everything inside. Three of the four bodies were burned so badly that investigators couldn't

immediately identify them. The jewelry, Jennifer Harbison, was wearing, had melted. The crime

scene was compromised in every way you can think of. Water, fire, smoke, contamination,

if you wanted to design a scenario where forensic evidence gets obliterated, this would be it.

The initial theory was that it was a robbery gone wrong. $50 was missing from the cash register,

...