The noise was enough to make Python swing round. Elissa leapt upwards and grabbed the Arrow. Python went for her, and Elissa threw the Arrow to Silvius, who caught it, just. Now Elissa had the Bow, and Silvius the Arrow, and Python was between them.

The rocks were rumbling. Tisamenos’s eyes were rolling into the back of his head, and he was trembling all over. There was a noise like a small landslide. The scree and rubble around them was quivering as if with its own life.

Elissa understood. The rocks were listening to him.

Tisamenos was commanding the stones. One by one they crept across the ground, until they began to pile up around Python’s feet, building a prison of rock, trapping him.

‘You’re doing it! Tisamenos, you’re doing it!’ They could defeat him. The possibility was suddenly in front of her. Python’s scaly body was disappearing under rubble, flints and stones surging, clambering over each other as if in a race to crush him.

But Python simply smiled.

And then he began to grow, the stones glancing off him like water.

‘Quickly! The Arrow! Throw it to me!’ Elissa cried, desperately trying to keep her self-possession.

Python’s bulk was now larger than a horse, and though the stones were still rushing towards him, they were uselessly deflected. Elissa stretched out to Silvius. This was their only chance, now. But instead of passing the Arrow to Elissa, Silvius hurled it as hard as he could at Python. What was he doing?

It flew true.

And it stuck, quivering, into his neck.

Everything seemed to stop, and Elissa was suddenly aware of the steady drip of water from the cave roof. Silvius, caught in a stance, both arms outstretched, his sandals loose, his knees grazed. Tisamenos, shaking on the cold ground.

Breaking the stillness, Python screamed, a terrible scream that echoed round the cavern. And then he tore the Arrow from his wound, gushing black smoking blood in gouts. With a great roar he snapped it in two.

The energy expelled from the Arrow blasted Elissa and Silvius to the floor.

‘It didn’t work …’ sobbed Silvius. ‘He’s still alive.’

Python’s features were contorted in rage. ‘You mortal fools …’ He ran at them, half-man, half-snake, and Silvius clutched Elissa, about to pull her out of the way.

There was no way out. Elissa braced herself.

And then Python choked and halted, slipping a little in his own gore. His expression changed to one of confusion. His feet started to fuse together, into the shape of a snake’s tail. He looked down in horror. His whole body began to shrink.

Soon he was the size and shape of a normal snake.

But it wasn’t over yet. The snake reared and hissed, swaying alarmingly.

‘Get him!’ Silvius cried, and hurled another rock at him.