Myrtilus was born the son of Hermes, the Olympian god who presided over thieves, travellers, merchants, and charioteers, a deity whose favour was as useful to the cunning as it was dangerous to the trusting. His mother was a mortal woman, a slave or a concubine in the household of Oenomaus, the king of Pisa in Elis, and Myrtilus grew up in the royal stables, learning the care of horses and the craft of the chariot from the men who prepared the king's war-car for battle and for sport. He was not a warrior himself but a mechanic, a man whose skill with wood and metal and harness was more valuable to the king than the strength of a dozen spearmen. The chariot of Oenomaus was famous throughout the Peloponnese, a vehicle drawn by divine horses, a gift from Ares, the god of war, that had never been defeated in a race, and Myrtilus was the only man who knew every joint, every pin, every strap that held it together.

The crisis of Myrtilus's life arrived in the form of Pelops, the Phrygian prince who came to Pisa to compete for the hand of Hippodamia. Pelops was handsome, wealthy, and desperate. He had seen Hippodamia and desired her, and he knew that the only way to win her was to defeat Oenomaus in the chariot race that had killed eighteen suitors before him. The race was simple in its cruelty: the suitor would drive away with Hippodamia in his chariot, and Oenomaus would pursue him in his own divine car. If the king caught the suitor before reaching the altar of Poseidon at Corinth, he would kill him with a spear through the back. Pelops knew that no mortal horses could outrun the steeds of Ares, and he knew that he needed help from inside the king's household. He approached Myrtilus with a bargain.

The bargain was specific and terrible. Myrtilus was to sabotage the king's chariot, replacing the bronze linchpins that held the wheels to the axle with pins made of wax. In the heat of the race, the wax would melt, the wheels would come loose, and Oenomaus would be thrown from the car and dragged to his death by his own horses. In exchange for this treachery, Pelops promised Myrtilus two things: half the kingdom of Pisa, and one night with Hippodamia, the princess whose beauty had driven nineteen men to risk their lives. Myrtilus, tempted by the kingdom and perhaps by the woman, agreed. He was the son of Hermes, after all, and the god of thieves did not raise his children to be loyal to kings.

The race took place on the plain of Olympia, and Myrtilus watched from the starting line as Pelops drove away with Hippodamia and Oenomaus pursued in his sabotaged chariot. The king's horses were faster, as always, and he was closing the gap when the wax pins began to melt. The wheels came loose, the chariot collapsed, and Oenomaus was thrown from the car and caught in the reins. His own horses dragged him across the rocks of the plain until his body was torn to pieces, and he died cursing the charioteer who had betrayed him. Pelops crossed the finish line, married Hippodamia, and claimed the throne of Pisa. The Olympic Games were founded on the grave of the dead king, and Myrtilus waited for his reward.

It never came. Pelops, now king and husband, had no intention of sharing his kingdom or his wife with a slave. He invited Myrtilus to a meeting on the cliffs of Geraestus, or in some accounts on a headland overlooking the sea, and there he confronted the charioteer with his treachery. Some versions say that Pelops accused Myrtilus of trying to rape Hippodamia, a charge that may have been fabricated to justify the murder. Others say that Pelops simply told Myrtilus that the bargain was void and that a traitor deserved no reward. Whatever the words, the result was the same. Pelops seized Myrtilus and threw him from the cliff into the sea below, and as Myrtilus fell, he cursed Pelops and all his descendants. The curse was absolute, a spoken doom that would pursue the house of Pelops through every generation.

The curse worked. Pelops and Hippodamia had two sons, Atreus and Thyestes, whose feud of adultery, cannibalism, and revenge produced the most terrible crimes in Greek mythology. Atreus killed the children of Thyestes and served them to their father at a feast. Thyestes raped his own daughter to beget a son who would avenge him. Atreus was murdered by his wife and her lover. Agamemnon, the son of Atreus, was murdered by his wife Clytemnestra on his return from Troy. Orestes, the son of Agamemnon, killed his mother and was pursued by the Furies to the edge of madness. Every tragedy of the house of Pelops could be traced back to the words that Myrtilus spoke as he fell, and the Greeks understood that a dying man's curse, spoken in the moment of his greatest injustice, was the most powerful magic in the world.

The sea into which Myrtilus fell was named the Myrtoan Sea in his memory, a stretch of water between Euboea and the Cyclades islands that remains dangerous to sailors even today. The name was his only monument, for no tomb was raised to him and no sacrifices were offered at his grave. He was a traitor who had been betrayed, a murderer who had been murdered, and the Greeks did not honour such men. But they remembered him, because without his curse there would have been no Oresteia, no Agamemnon, no tragedy at all. Myrtilus was the spark that lit the fire that burned the house of Pelops to the ground.