A tomb of 49,000 year-old Neanderthal bones discovered in El Sidron, a remote, mountainous region of northern Spain, leads to a compelling investigation to solve a double mystery: How did this group of Neanderthals die? And could the fate of this group help explain Neanderthal extinction? Scientists examine the bones and discover signs that tell a shocking story of how this group may have met their deaths. Some bones bear distinct signs of cannibalism. Was it a result of ritual or hunger? Neanderthal experts are adamant that they were not bloodthirsty brutes. What happened here 49,000 years ago will take viewers on a much bigger journey - from El Sidron to the other end of the Iberian Peninsula, where scientists are excavating beneath the seas off Gibraltar in search of Neanderthal sites.