High in the Austrian Alps, Lake Toplitz has drawn treasure hunters for decades on the strength of a wartime legend: that retreating Nazi officials sank crates of gold and secret Third Reich documents into its black, oxygen-starved depths before the collapse of the regime. The film traces the story back to the so-called Alpenfestung, the planned Alpine Fortress where high-ranking officials like SS officer Ernst Kaltenbrunner and commando leader Otto Skorzeny were meant to make a last stand, and asks how much of that plan was real versus propaganda. It follows the postwar decades of diving expeditions into Toplitz's freezing, snag-filled waters, some of which ended in drowning, and weighs what divers actually recovered against what legend insists is still down there. Interviews and archival material sort documented salvage operations from decades of rumor, tracking how a scenic lake became a fixture of Nazi-gold mythology. The film treats the mystery as still open, laying out what has been found, what has not, and why the search never really stopped.