Cadmus had a sister named Europa. She was carried off by Zeus, who was disguised as a bull, and became the mother of King Minos of Crete. When Europa disappeared, Cadmus went in search of her. For many months he scoured the lands around his home, but he could find no sign of his sister. At last he went to Delphi to consult the oracle, where the advice and prophecies of the god Apollo were revealed.  Cadmus asked the oracle what he should do.  "Your sister is safe. Search for her no more," said the oracle. "Your destiny lies elsewhere.  When you leave here, you will see a cow.  Follow it, and when it falls to the ground, exhausted, there you must build a great city."

Outside Delphi, Cadmus saw a cow, just as the oracle had promised. With a group of men he followed it for many miles until at last it sank to the ground. "Here we will found our city, and call it Thebes ," said Cadmus.  "But first, we must sacrifice this cow to thank the gods for their guidance.  Go and fetch some water from the spring to honour them."  When his men took water from the nearby spring, they disturbed a terrible serpent.  It killed them all with its fearsome, snapping jaws.  In fury Cadmus slew the serpent with a blow from a huge rock.

Grieving for the loss of his men Cadmus went ahead and sacrificed the cow.  The goddess Athena appeared and told him not to worry.  "I will supply you with better men than any king can command.  Just take the serpent's teeth and sow them in the soil!"

Cadmus did as he ws told, and from the soil sprang fully grown men, warriors all. Before the men could turn on him, Cadmus threw a stone among them, and they fought so fiercely about who had thrown it that in the end only five survived.  Cadmus made peace with them, and these warriors, the strongest and the fiercest of all the sown men, helped him establish the great city of Thebes.