Tisamenos gasped, as it flung up its head and opened a pair of large, leathery wings, hissing and showing sharp fangs. It pounced so that it landed on all fours, looking up at them, yanking at the chain, grunting, and Tisamenos was relieved to see that it was firmly fixed to a huge, solid ring.

‘What is it?’ he whispered. The second beast, he thought. He shivered. Was his father bringing him here to fight it? Was this another test? The thing hissed again, and lashed its long, whip-like tail back and forth.

‘The House Accursed,’ said Orestes. ‘When I … avenged your grandfather, the gods released the Furies. They tormented me, night and day, until …’

‘Until you went to Athens, and Athena absolved you, and the Furies were chained up under the Temple of Justice,’ finished Tisamenos. He knew the story well. Or at least he thought he did.

‘You have learned your lessons,’ said Orestes. ‘So they were. Two of them, at least. But what nobody knows – nobody else, not Electra, not Hermione, not Erigone – is that I was not fully absolved.’

Tisamenos felt dizzied. His father was giving him knowledge that nobody else had.

‘My crime was too great. To kill a mother …’ His voice broke a little, and he turned his eyes full onto his son. ‘I hardly knew her. She wasn’t my mother. I had no memories. She was a symbol. I had to kill her, for myself, and for my father. And for Electra, of course … she goaded me on. I do not blame her, Tisamenos. I do not blame anyone. It had to happen that way, and no other.’

Erigone was a mother, too. Little Penthilos, wrapped in soft linen. Was it any of his fault? What would revenge cost him?

The beast snarled, and shook its wings.

‘I was forced to keep one of the Furies here, in the foundations of this terrible house – a constant reminder of the pollution that I loosed upon the world. I’d hoped you would never know, never see, because the Fury will go when I die. But now …’

He moved to one side, and the Fury followed him, revealing behind it a long, narrow ledge, on which was a box.

‘I swore an oath to Apollo, Lord of Light. I swore to him that I would do everything I could to purify the world, to try to blot out the stain I had made. And he gave me something to guard.’

Orestes reached out, and the Fury, growling, let him pass. Trembling, he took the box, and moving nearer to the stairs, showed it to Tisamenos.

‘What is it?’ the boy asked, reaching forward to take it. Orestes pushed him out of the way, just in time, as the Fury lashed at him. Springing back, he watched warily as she skittered her claws on the ground.