In 1241, the Mongol army had just annihilated European forces at the Battle of Legnica and stood virtually unopposed on the road to Paris — then inexplicably turned around and never came back. Historians credit internal politics, but the real answer might live in a single sentence buried in a Hungarian chronicle about a sick horse, a flooded river, and one general's superstition about omens. This week, we pull on that thread — and the Europe that almost wasn't.