"20/20" investigates the mystery of a body found in a barrel at Nevada's Lake Mead.

As Environmental Crises Cause Las Vegas Reservoir To Recede, a Trail of Bodies From Decades Past Is Revealed

One-Hour '20/20' Features Exclusive Interviews With Niece of Alleged Mob Whistleblower and Former FBI Special Agent

Program Airs Thursday, May 4 (10:01-11:00 p.m. EDT), on ABC, Next Day on Hulu

Since the 1930s, Lake Mead - a picturesque reservoir outside of Las Vegas - has been the site of over 300 drownings, making it one of the deadliest lakes in America. However, it wasn't until recently that Lake Mead's truly sinister history came to light. As environmental crises like drought, warming temperatures, and diminishing water supply have caused the reservoir to recede, people have discovered bodies in the lake. In a special edition of "20/20," ABC News contributor Chris Connelly investigates the secrets of Lake Mead and details how authorities are using DNA evidence to crack cases that had long gone cold.

The program features an exclusive interview with Patricia Haas, who details her tireless journey to solve the mysterious disappearance of her alleged mob-linked uncle at Lake Mead. "20/20" also has an exclusive interview with former FBI Special Agent Deborah Richard, who provides insight into the history of organized crime in Las Vegas. Additionally, the one-hour special has interviews with officers from the Las Vegas Metro Police, families of the victims of Lake Mead, Lake Mead experts and Las Vegas historians. "20/20" airs at 10:01 p.m. on Thursday, May 4, on ABC, next day on Hulu.

ABC News' "20/20" is an award-winning primetime program anchored by David Muir. A proven leader as a long-form newsmagazine for over 40 years, "20/20" features unforgettable, character-driven true-crime mysteries, exclusive newsmaker interviews, hard-hitting investigative reports and in-depth coverage of high-profile stories. Janice Johnston is the executive producer. The two-hour "20/20" events air Fridays from 9:01-11:00 p.m. EDT on ABC and are available to stream on ABC News digital platforms and Hulu.