As soon as they reached Macro and Sempronius, Cato thrust Julia and her maid down on to the deck and took up the tail end of the rope Macro had used to secure himself to the mast. Glancing up, he saw that the wave was much closer now, travelling at an extraordinary speed as it swept along the coast. He snapped round to the two women.

'Raise your arms!'

Running the rope round their stomachs, Cato circled the mast and tied the end into the loop round Macro's waist.

'What about you, lad?' Macro looked up anxiously.

'I need more rope.' Cato stood up and glanced round. Every spare length seemed to have been taken. Then his eyes caught sight of something over the side of the Horus, no more than fifty paces away in the sea. The glistening tip of a rock was exposed above the surface, and as Cato looked, more rocks emerged. Closer to the shore it seemed that some tidal current had drawn the water away, laying bare reefs and even the stunted upper works of an old wreck. The sight astonished him for an instant before a terrified shout from one of the crew snatched his attention back towards the wave. It was visible to everyone on the deck now. A great dark monster, crested with a haze of white spray as it came on in a rippling, glassy mass, straight towards the Horus. Ahead of it, the tiny wings of a seagull glimmered in the fading glow of the sunset, then the bird was lost in the shadow of the wave.

'Cato!'

He turned and saw Julia staring at him, struggling to reach out and grasp his hand. Cato knew there was no time to tie himself down. It was too late for him. He slumped down on the deck and squeezed himself between Macro and Julia as best he could, grasping them both round the shoulders. The light breeze that had been blowing along behind the ship abruptly died and the sail sagged like old skin from the spar, before suddenly being taken aback as the wave thrust the air ahead of it. The great mass of water rose up ahead of the ship, high, higher than the mast, and Cato felt his stomach knot as he gritted his teeth and squinted at the oncoming monster.