It started with a party, high school seniors celebrating graduation. Before the night was through, one man was dead and two teens were facing a long fight for justice.

The fire broke out before dawn. After the smoke cleared, a mother of two young children was found dead. It was the tragic end to a life that held so much promise, but for investigators, it was just the beginning. Was this an accident or murder?

Kevin and Morgan Mengel were happy at first, but when the marriage went bad, he went missing. Police wondered if he simply left, but a family’s relentless pursuit lead to a stunning confrontation and, eventually, the truth.

A family mourned the loss of a young mother in a house fire. Authorities ruled it an accident. Then, years later, there was another accident and second loved one was gone. Was this just a string of bad luck or the work of a calculating killer?

She was a savvy entrepreneur. He got his start in finance. Their connection was instant but when their summer love cooled, tempers flared and the relationship took a tragic turn. It seemed like an open and shut case but there was a surprise in store.

The doctor and the model made a stunning couple. Together they built a loving family. Her death was sudden but ruled natural causes. Secrets remained hidden for years. Then, her daughters became amateur detectives to help unlock the mystery.

Aasha Davis moved to Hollywood with big dreams. Her sister Lesley followed for support. Then, Lesley went missing and Aasha was desperate to find her. In a town built on deception, police came up with a high-stakes plan to smoke out their suspect.

It was just before Halloween. Joel Lovelien and his fiancee headed to a local bar packed with people in costume. Then, Joel stepped outside and walked into a troubling mystery. Police rounded up potential suspects, but could they unmask a killer?

Keith Reed was a highly-regarded school superintendent. When he didn't show up at an out-of-town conference, it set off alarm bells. Investigators took a hard look at his love life for clues and made a startling discovery.

Kelli Bordeaux was just starting what she hoped to be a long career in the military, but fate had other plans. When she vanished, friends and family launched a frantic search, but it was stranger hell-bent on justice who uncovered the ugly truth.

Sandra Galas was born and raised in paradise. So how did something so ugly happen there? Police investigated two men in Sandra's life, but the case went cold. Her father refused to give up, relentlessly pursuing the truth for more than a decade.

Diane McIver was a successful businesswoman who enjoyed a lavish lifestyle with her husband. Then she was gone. It was a mystery riddled with privilege and power, but investigators needed to answer a crucial question: was this an accident or murder?

She was a divorced mother excited about her next chapter in life. Then, five gunshots shattered her plans. Proving who murdered Joan Lockwood was a daunting task for police. An ominous killer was still out there and her family was living in fear.

Detectives believed two young children witnessed the unthinkable, the brutal murder of their mother. The prosecution's case would be built around what they thought those kids observed, but was another version of events possible?

This is a story of teens, text messages and a complicated search for the truth. Conrad Roy had vanished. Turns out, he shared a secret with someone close to him. What that confidant did and did not do with the information shattered two families.

Amanda Lindhout was a journalist braving the world's most dangerous hotspots. Then, she became the story. What she endured from her captors was terrifying. Years later they found her again and secret agents put a daring undercover sting into action.

For over a decade, El Chapo evaded authorities but one man was determined to catch the infamous kingpin. Former DEA agent Andrew Hogan comes out of the shadows to detail his search and capture with never-before-seen videos and photographs.

Angel's Landing was a community of free-spirits with Lou Castro at its center. Investigators were suspicious of the mysterious deaths happening there. Now, commune members have courageously decided to tell their stories in hopes of helping others.

This is a story about faith, temptation and secrets. A churchgoing mom was shot at point-blank range in her garage. Saving her would take a miracle and investigators wanted to know if this crime was random or if someone wanted her dead.

He was the hardworking dad, she the doting mom. In the still of the night, strangers armed with knives destroyed all they had built together. Turns out, someone was hiding an ugly secret. Police would hatch an elaborate plan to uncover the truth.

She was a young mom, pregnant with her second child, when she was gunned down on her way to work. Police zeroed in on the men in her life. To help find her killer, her sisters became amateur detectives and uncovered a secret.

Dateline has been covering this twisted tale for more than a decade. Pizza deliveryman Brian Wells robbed a bank with a bomb locked around his neck and, from there, it turned into one of the strangest cases the FBI has ever encountered

A bank executive tries to rob his own bank. Investigators think it is an inside job but eventually learn the crime is connected to a spree carried out by men who managed to keep their identities secret, praying on people who did the opposite.