Filled now with a kind of exultation, Tisamenos herded Erigone into the hidden corner with the secret door. Erigone, at bay, turned to face her pursuers, Silvius with his sword raised, Elissa poised to block her way if she tried to run.

Erigone’s eyes glinted cruelly in the torchlight. Straight and tall, she did not waver.

‘If you kill me now, in this place, my ghost will haunt you,’ she said.

‘I will not kill you,’ said Orestes. He pressed the spring that opened the door. ‘Go down.’

‘Exile me. Send me away. I will go to the furthest north.’

‘You must go down.’ Tisamenos’s voice was cold and hard now.

She had no choice. She went into the room where the black cube sat, its terrible pictures stark in the flickering flames. This time Tisamenos struck the mechanism, and opened a panel in its side.

‘Down,’ said Orestes.

‘What is beneath?’ Erigone was still proud, and did not betray her emotion.

‘Your fate,’ said Tisamenos. A stench reached their nostrils, rank and strong. Silvius spluttered, and Elissa coughed.

Tisamenos went first with a torch. He could hear the clink of the chain as the beast sensed them. Then Erigone followed him, stiffly, but holding her hands over her mouth against the smell. Orestes followed her, and Silvius and Elissa, looking suddenly small and young, came after.

This was what the stones wanted, and this was how he would end the cycle of horror that had haunted his house.

The chamber below was black as the night sky. Erigone, pride still ringing, said, ‘You cannot do this to me!’ Orestes seized the torch from Tisamenos.

‘See, Erigone,’ he said, ‘see the curse of the House of Atreos.’ Tisamenos watched Erigone as the torch lit up a recumbent form. His stepmother let out a terrified moan as the light touched the Fury, as it unfurled wings, leathery and huge, and twisted round to face them, a terrible distortion of a woman, a lizard, a dragon, a monster, its teeth huge and dripping, its eyes yellow and pitiless. It sniffed the air, and screamed, pulling on its chain.

‘What is that?’ Silvius’s horrified face was like a mask.

‘It is from the Underworld …’ Elissa spluttered.

‘So it is true …’ Erigone gasped. The Fury pawed at the ground, its claws scraping. ‘They said there was a Fury here … I did not think it possible …’ Her voice was trembling now, betraying her fear.

She tried to run up the stairs, but Tisamenos grabbed her by the elbow. She snarled at him, scratching with her long nails. He held firm.

Orestes approached the Fury. With a low growl, it slunk aside for him, its huge shape retreating and coiling round like a snake. Releasing Erigone, Tisamenos saw his father take the box from its place on the ledge. He lifted it up in triumph, and showed it to Erigone.