In June of 323 BCE, Alexander the Great died in Babylon. He was thirty-two.

He had taken the known world from the Adriatic to the Indus in a decade. He had crossed two continents at the head of an army. He had survived a near-drowning in an icy river, a stone to the head, and an arrow through the lung. And then, over the course of eleven or twelve days, a fever did what no army had managed. The most powerful man on earth was dead before his next campaign began.

We have several accounts of those final days, written by historians who were not there. We have a strange chain of rumors about poisoning, a court full of plausible suspects, and a body that — according to one source — did not begin to decompose for six days.

The suspects are ancient. The arguments are not.

In the summer of 430 BCE, something horrific tore through Athens.

The city was at war with Sparta, packed beyond capacity with refugees from the countryside, and entirely unprepared for what came through its gates next. Within four years, perhaps a quarter of the population was dead, including the man who had led Athens into the war. We have an eyewitness account of the disease from Thucydides, who caught it himself, and survived to write it down.

We have, in the last twenty years, fragments of DNA recovered from a mass grave of its victims.

However, we still cannot agree on who, exactly, was the killer.

This episode walks through the candidates: typhus, typhoid, measles, and a few stranger guesses — and asks what the evidence will and will not let us conclude. One of them has been the leading suspect for almost a century. One of them has direct molecular evidence behind it. They are not the same suspect, and that is where the trouble begins.