He bounced down another couple of metres, halfway down the cliff, the hammer in his left hand. Suddenly a grip like a vice held his left ankle, and he began spinning wildly. He looked down. A figure in a black wetsuit was staring up at him, wearing a close-fitting diving mask, legs wrapped around the rope just above the step. One hand held Jack’s ankle and the rope, the other held a silenced pistol, aimed at Jack’s head. ‘Give it to me,’ the man said coldly, in a thick Italian accent. Jack looked down, saying nothing. A bullet cracked past his face, followed by the thump of the silencer. It was a warning shot. Jack caught sight of something out of the corner of his eye, a shape. He swung, and aimed the hammer at the man’s head, a killer blow. But the arm holding his ankle was closer, and he brought the hammer down hard against the man’s wrist. There was an explosive sound as the bones snapped, and the pistol spun off into the cavern. Simultaneously Costas launched himself at the man’s legs, bringing him down with a huge crash. The man tried to get up, tripped, tumbled down and hit the channel below with a sickening crack, and then was gone, swept away down the tunnel in the torrent. Jack dropped down to help Costas, who had also removed his respirator and visor. ‘You okay?’
‘Fine,’ Costas panted. ‘Only wish you’d put that hammer in the little bastard’s forehead.’
‘I don’t think he’ll be troubling us any more,’ Jack said.
Costas wiped some blood off his mouth and looked down. ‘Well and truly flushed out.’ He looked back up the cliff face. ‘Right. Hook me up. That’s done it for me. The sooner we get what we’ve come for and get out of here, the better.’
Twenty minutes later they were in a narrow space above the final flight of rock-cut stairs. Jack squeezed himself as far up the crack as he could go, his arms raised above him into a hollowed-out chamber. He could feel nothing. He wriggled further, but it was no use. His head was jammed sideways against the top of the crack, and all he could see was the side of the jagged fissure inches from his face. He felt blindly with his hands, but there was only empty space. He arched his back, pushing hard, and felt himself move fractionally forward, an inch or two. Suddenly his fingers met resistance. Wet rock, smoothed down, different from the irregular rock of the fissure. He parted his hands and felt around. It was a circular chamber, about two feet wide, sunk into the rock. He felt down as far as he could reach, and touched the base of the chamber. He traced his fingers slowly around the edge. Nothing.
It was empty.
Jack slumped slightly, and peered down at Costas’ face, just visible below his feet. ‘I can feel the chamber.’ His voice sounded peculiar, resonating in the chamber but then deadened in the fissure. ‘It’s a cylindrical hole bored into the rock. I can feel all round the base. There’s nothing inside.’
‘Try the middle.’ Costas’ voice sounded distant, muffled. ‘Maybe there’s another smaller chamber sunk below it.’
Jack shifted as far as he could to the right. He slowly drew his left hand across the bottom of the chamber. It was wet, slimy, with small ridges and furrows, as if it had been left roughly finished. He reached the other side. Suddenly he pulled his hand back again. There was a regularity to the furrows. He felt around, his eyes shut, tracing the marks, trying to read what he was feeling. There was no doubt about it. ‘You’re right,’ he said excitedly. ‘I can feel the outline of another circle, an inner circle on the floor of the chamber. I think it’s a lid, a stone lid. I can feel markings on it.’
‘Is there a handle?’ Costas said.
‘Nothing. It’s flat across the top. I’ve no idea how we’re going to open this.’
‘And those markings?’
‘I can count twenty so far,’ Jack said. ‘Wait.’ He flinched in pain as he jammed his elbow against the crack, trying to feel every part of the lid surface. He worked his hand round. ‘No, twenty-three. They’re in a circle, around the edge of the lid. They’re letters, raised letters carved on little blocks, set slightly into the stone surface. It’s curious. I can actually press them down slightly.’
‘Can you read them?’
Jack traced his fingers around the letters. He suddenly realized what they were. ‘It’s the Latin alphabet, the alphabet of the later Roman Republic and the early empire. Twenty-three letters. Alpha to zeta.’
‘Jack, I think what you’ve got there is a combination lock, Roman style.’
‘Huh?’
‘We studied these things at MIT. Ancient technology. If there isn’t a handle, the lid must have some kind of spring opener, set underneath to push it up. My guess is a bronze spring, set around the edge of the inner chamber. The letters must be a combination lock, probably attached to stone or metal pivots that secure the lid into the rock. The combination might be adjustable, allowing the person using it to reset it each time with a new code. Press the right combination, and bingo, the lid springs up.’
‘Twenty-three letters,’ Jack murmured. ‘And no way of knowing how many we need to press. I don’t even want to begin to calculate the number of possibilities.’
‘Let’s start with the obvious,’ Costas said. ‘It was Pliny the Elder who put the scroll here, right? What was his full name?’
Jack thought for a moment. ‘Caius Plinius Secundus.’
‘Okay. Punch in the initials.’
Jack pictured the Latin alphabet in his mind’s eye, and traced his finger around the circle until he came to each letter. C, P, S. He pressed them in the correct order, and they depressed very slightly, but no more. He tried again, then in a different order. Still nothing.
‘No good,’ he said, his teeth gritted.
‘Then your guess is as good as mine,’ Costas said. ‘You may as well try random combinations. We shouldn’t be here for more than a week. We really need to get going, Jack. Our friend might not be the only one. We don’t know.’
‘Wait.’ Jack’s mind was racing. ‘You might have the right idea. Let’s think about this. Pliny gets the document from Claudius. He promises to hide it away. Pliny keeps his promises, and never puts anything off. He’s got too much else to do, managing the naval base, writing his books. He takes his fast galley up to Rome that night, 23 August AD 79, right up the Tiber, comes straight here to the Admiral’s safety deposit box, returns that same night to Misenum on the Bay of Naples, just in time for the eruption. Whose name is fresh in his mind?’
‘You mean Jesus? The Nazarene?’
‘Not enough there for a code, and it might be too obvious. No. I mean Claudius himself. His name before he became emperor. Tiberius Claudius Drusus Nero Germanicus.’ Jack shut his eyes again, moved his hand over the letters and pressed them in. T, C, D, N, G. Nothing. He repeated it. Again nothing. He exhaled forcibly. ‘No good.’
‘Maybe you’ve missed a letter. Emperor?’
‘ Caesar Augustus.’ Jack found the letters, then punched them. Still nothing. He slumped again, then suddenly drew his breath in sharply. ‘No. Not Caesar Augustus. Claudius was no longer emperor. He would have been at pains to tell Pliny that. Not an emperor. He’d become something else. Something that would have amused them both.’
‘Claudius the god,’ Costas murmured.
‘ Divus.’ Jack reached back around and found the letter D. He pressed it as hard as he could. Something gave way, and the letter depressed at least an inch. Suddenly the lid sprang up, and Jack quickly withdrew his hand to prevent it being trapped. ‘Bingo,’ he said excitedly. He put his hand back where the lid had been. He could feel the coil of a heavy bronze spring, now holding the lid a foot or more above the opening it had covered. He reached inside and felt a cylindrical shape, loose in the hole. His heart began to pound. He pulled it out, easing it between the metal coils of the spring. The cylinder was heavy for its size, made of stone, about ten inches long and six inches wide. ‘I’ve got it,’ he said, pulling the cylinder out of the chamber and into the fissure, then holding it under his headlamp. ‘It’s Egyptian, a hand-turned Egyptian stone vessel. We’ve hit paydirt, Costas. It’s identical in manufacture to those larger jars in Claudius’ library, the reused canopic jars, the ones holding the papyrus scrolls. The lid’s still sealed in resin. Looks like Pliny didn’t tamper with it. We might be in luck.’ He passed the cylinder down to Costas, who reached up from the tunnel below. Jack eased himself back down the fissure, and the two of them squatted over the cylinder in the darkness, their beams illuminating the mottled marble surface as Costas turned the object over in his hands.