Clay-covered bodies squeeze through narrow rock passages. Sparingly lit by their helmet lamps, they blend in with the sediment-covered cave walls. The film accompanies a group of cave explorers and looks at their different motives for venturing into the inaccessible depths. In the farthest corners of the "Windloch" cave, discovered in 2019, lies a chamber filled with bizarre, delicate aragonite crystals. The most extraordinary of these is called "Hydra" by its discoverers.