Echoes of the Unknown

In today's episode, we’re traveling back to the Chicago suburbs in 1982, when seven people died after taking Extra-Strength Tylenol that had been deliberately laced with cyanide. Most of the victims had no connection to one another, and the killer never had to confront them directly. Instead, poisoned capsules were placed back on store shelves, turning one of America’s most trusted medicines into a murder weapon. To this day, the killer remains unknown.

In today's episode, we’re traveling to Vermont in 1946, where college student Paula Jean Welden set out alone for an afternoon walk in the Green Mountains. Several people saw her along the way, but after reaching the Long Trail, she disappeared. No confirmed trace of her has ever been found. Paula's disappearance would become one of Vermont’s most enduring mysteries — and the troubled investigation that followed would help change law enforcement in the state forever.

In today's episode, we’re traveling to California in 1978, where five friends set out together one Friday night. They drove to a college basketball game, stopped at a market for snacks, and began the trip home... but they never arrived. Days later, their car was discovered abandoned, high in the Sierra Nevada foothills, on a remote mountain road they had no reason to be traveling. Months later, four of the five men would be found dead under perplexing circumstances — the fifth would never be found.

In today's episode, we're traveling to Germany in 1984 to examine one of the most perplexing mysteries in modern German history. It began with a food technician's cryptic handwritten message, and ended with a series of inexplicable events. The man's death baffled investigators for more than four decades as they struggled to explain what happened to him. His strange final hours continue to fascinate everyone who has studied this extraordinary case.

In today's episode, we're traveling to Oak Island, off the coast of Nova Scotia. For more than 230 years, treasure hunters have been drawn there by rumors of a vast hidden fortune buried deep beneath the earth. They've spent millions of dollars, employed some of the most advanced technology of their time, and endured repeated setbacks in pursuit of a secret that has stubbornly refused to reveal itself to this day.