On January 26, 1966, three siblings—Jane, Arnna, and Grant Beaumont—left their home for a short trip to Glenelg Beach in Adelaide.They never came back.What started as a normal summer day quickly became one of Australia’s most chilling and enduring mysteries. Witnesses saw the children playing with an unknown man. Hours later, they were gone—without a single trace.No bodies. No confirmed suspect. No answers.For nearly 60 years, investigators have searched, excavated, and followed countless leads… yet the truth remains unknown.In this episode of The Unknown Files, we break down the timeline, the suspects, and the theories behind one of the most haunting cold cases in history.Someone knows what happened.