Dateline: Secrets Uncovered - Season 4

Michelle Young was married to her college sweetheart and pregnant with their second child when she was murdered. In the search for her killer, detectives uncovered a marriage riddled with secrets but cracking this complicated case took years.

How well do you really know your neighbors? It's a question at the center of this mystery. The neighbors you're about to meet enjoyed mixing business with pleasure then a murder made them face the reality that a killer was in their midst.

Judy Carlson lived in a painful limbo. Her son disappeared without a trace. Years went by and she may never have known his fate if not for a rookie detective's dogged work but to solve this cold case, the investigator also need the help of a killer.

Steven B. Williams was a DJ with a golden voice. Then he vanished. It was a mystery that stretched from California to Montana, and the clue to it all? It was wrapped in a napkin, tucked in a cabinet, hidden in a library, but would anyone find it?

Jack Jessee was a family man who didn't seem to have an enemy in the world, up until the night he was killed. Was someone carrying a secret grudge? The case went cold but a relentless detective was determined to catch Jack's killer

Soon after Angie Dodge was murdered, Christopher Tapp admitted he was one of her killers. Police captured his confession on videotape so why would the victim's mom, who once campaigned to put Tapp in prison, now be fighting for his freedom?

Larry McNabney had a thriving career and a wife he adored. Then he vanished. It was a mystery as twisted as they come. At its center: three lives tangled together in a love triangle, including one of them who was hiding a secret identity.

When Karen Pannell was found stabbed to death, a message scrawled in blood seemed like a beacon that could lead detectives to her killer. But what exactly did it mean? It would take a dogged forensic specialist with a keen eye to unravel the mystery.

It was a mystery that stumped investigators for years. A college student disappeared after a night out clubbing. Her mother thought she was at a sleepover with friends and it took an eagle-eyed detective to find the truth buried in a pile of lies.

A young mom, married to her high school sweetheart, vanishes. Did she leave her family to start a new life or was there another reason for her disappearance? Decades later her grown son faced a dark truth at the core of this mystery.

She was a dancer who married a dashing photographer. They seemed to have the picture-perfect life -- until the bone-chilling night she disappeared. In a case filled with twists, could the victim help solve her own murder?

A former homecoming queen taking her first steps into adult life is brutally murdered. Who would want to harm her? The investigation centered on two men and a mysterious black bag that seemed to come out of nowhere.

It was a brutal and baffling crime: a husband shot dead in his own bed. No one else in the house was hurt, not even his wife, who was sleeping beside him. Investigators were suspicious, but there were more surprises in store.

It's a mystery with a mind-boggling twist. The deputy warden's wife claimed she was kidnapped by an escaped convict and held captive for more than a decade. But was she really a hostage or a willing accomplice?

A smooth convict was offered a deal as tempting as it was dangerous: get key information from a suspected serial killer to win your freedom. The catch? He'd have to go undercover in a psychiatric prison with no guarantee of getting out alive.

When the wealthy heir to a legendary hotel is murdered, the list of possible suspects is long. He had his share of enemies, and a complicated family. Investigators soon learned someone close to the victim was also in danger.

It's a true Hollywood whodunit. A show business stuntman was shot four times and left to die. Investigators uncovered a love story gone wrong and a villain with a dark secret. But the most stunning twist of all is what didn't happen.