Tisamenos felt his sinews stiffen. ‘Father – Mother. I have to show you something. It is time for the truth to be known.’ He laid a palm on the stone door of the tomb, and then took Erigone’s hand. She flinched, but he held it tightly. ‘Father, please put your hand on your wife’s.’ Orestes, gazing anxiously at his son, did so.

The stones were part of him now. They were in him, and they spoke through him. In the cold halls of his mind, his father and his stepmother now appeared, and they saw what he saw.

He felt an insidious sense of power dancing ahead of them in the corridors, shouting, ‘Follow! Follow!’ They had no choice but to do so, pulled along by the force of the stones, as Tisamenos closed the way behind them.

The stones showed them everything. First, the wicked Tantalos, grinning in his foulness, standing triumphant before a table groaning with slaughter. Then Atreos and Thyestes, clothes and faces spattered with blood.

What came next was closer to home. They paused on the steps of the kinghouse.

It was a hot afternoon. Flies buzzed above an old dog who slept, whimpering slightly, in the shade. A soldier, back from the war, was greeting his daughter, his weary face relaxed at last, marvelling at how she’d grown in the ten years since they’d sailed for Troy.

King Agamemnon was entering into his bathhouse, followed by Cassandra, her Trojan robes bright. He took off his war gear, let himself gently into the bath, allowing Cassandra to wash the back of his neck, his shoulders. Tisamenos saw war being eased away from his grandfather. Cassandra began to sing something, a Trojan lament, and Agamemnon grabbed her hand as if to stop her.

The door opened, a wedge of light spilled across the floor, and then a net was thrown over the king and his concubine. A dagger, and a sword, and the bathwater dripping red.

Tisamenos heard Orestes sob.

But they had to go on.

And now, years later, a boy not much older than Tisamenos, in armour that didn’t fit him properly, was standing in the hall of his ancestors. His sister Electra was goading him onwards. He stood, irresolute, before making a decision and marching into Clytemnestra’s chamber.

There was a terrible cry, and it was Clytemnestra, and it was Orestes too. ‘Snake!’ came a shout from the queen.

A moment later, the boy was staggering out of the room, a bloody mark on his face, his expression aghast; then Aegisthos was rushing into the hall, unarmed, and Orestes was blindly, furiously, slaying him.

‘You’ve seen it now,’ said Tisamenos’s father behind him. ‘You’ve seen what I did.’

Then they saw the daughter of Aegisthos, Erigone, sole survivor of her family, always in the shadows, watching as Orestes married the beautiful Hermione and bore him a handsome son, nursing revenge in her heart.