In 1993, a group of archaeologists found the CACAO site, a unique cave in the Argentine Puna. Ten years later, archaeologist Carlos Aschero finds a rib of the Mylodon, an extinct mammal from the Ice Age. The rib has marks that suggest human intervention and gives a date of 40,000 years, which surprises locals and strangers. The story narrates the adventures and misadventures of that group in the face of a unique discovery that questions what we know about the settlement of the American continent.