'Come,' I said. 'Quickly-or we'll drown!'

But she broke my grasp and scooped an armful of papers at random from the coffin, which now balanced precariously on its stand. 'The papers,' she said. 'Help me!'

But I was not going to drown for the sake of Sir Ambrose Plessington. I stepped forward and, seizing her arm, pulled her towards the threshold. The papers clutched to her chest spilled into the water, then the ink blurred and ran on the parchment, effacing itself in the eddying current. I could see among those sodden scraps the paper recovered from the galleon-the secret of the Sacra Familia once more cast upon the waters.

It would not be retrieved a second time. I reached down the lantern and, still clutching Alethea's arm, forced the door a few inches wider. The water must have broken through elsewhere in the crypt, for in the corridor it was two feet deep and flowing in a torrent from the direction of the staircase. Thrusting the lantern aloft I tried to make out the distant stairs. Already my feet were numb. I could hear the water whorling in the corners and slapping against the copper-sheathed walls. I swung round to face her.

'Is there another way out?'

'No.' She was still struggling to salvage what remained of her father's papers, which now flowed past like trout in a brook, trailing seals and ribbons. 'Only the way we came!'

I dragged her away and waded knee-deep into the current. The water was black now instead of red. After a few steps I heard the coffin fall from the trestle-table and overturn. I pressed forward. When I raised the lantern I saw that the other doors in the tunnel had burst open under the tremendous force of the waters. Their tributaries deepened and quickened the flow. Soon the fragments of wooden barrels and hanks of old rope were washed into our path, followed by the bone-urns from some ancient ossuary. Then came the bones themselves, bobbing skulls and femurs, the jumbled remains of a hundred monks shifting and sliding towards us.

I picked my way round the grotesque flotsam with Alethea still in tow. We had no more than a minute, I reckoned, to make our escape, before the crypt filled with water. When the water reached the middle of my thighs I heard another noise, a frantic squeaking which I mistook for the hinges of the lantern until I saw dozens of rats-fat, matted creatures-swimming against the tide and using the floating casks and skulls as stepping-stones. I lost my footing, then my grip on the lantern, which toppled into the water and extinguished with a hiss. I could see nothing in the darkness but, far in the distance, a weak light from the hatchway glowing overhead. I began struggling towards it, but so weakened was I when we reached the stairs that I could barely stand. The water had risen to my chest; it took three attempts before I finally found purchase on a submerged tread. Then I gripped the banister and climbed hand over hand until, exhausted and frozen, followed by Alethea, I breasted the hatch.

The corridor was running with water, adding to the torrent in the crypt below. We staggered towards the atrium, passing on the way the breakfast parlour and the Great Room. In the latter the cornices and their brackets were streaming, as were the stalactites of lime-washed plasterwork. A segment had fallen from the centre of the ceiling exposing the laths and joists beneath. Cracks like lightning-strokes had begun appearing on the walls, spilling yet more plaster in the water. Then, over the rush of water, we heard a desperate voice-that of Phineas-summoning Lady Marchamont.

'The books!' Alethea was saying over the roar of the water behind us. 'We must rescue the books!'

But we were not to reach the library, or not just yet. For on stumbling into the atrium we discovered Phineas with his back turned towards us, endeavouring to block the entrance door as he had done against me. It was shaking in its frame under some furious assault from the outside. He had no better luck the second time, for after another blow the door burst wide with a shriek of tortured wood and a gust of wind. I heard the crystal pendants of the chandelier chiming high overhead and felt Alethea's frigid hand in mine. Our visitors had arrived at last.

It was their coach, framed in the doorway, that I noticed first: a fleet-looking vehicle with a domed roof and four horses stamping and foaming in their traces. Then I heard a crunch of gravel and a broad figure stepped through the splintered frame, followed swiftly by three men in black-and-gold livery.

'Sir Richard?' Alethea was standing stock-still and open-mouthed beside me. Was she remembering the murder on the Pont Neuf? Quickly she dropped my hand. 'What are you doing here? What is-?'

Phineas was the first to respond, scuttling forward to grapple with one of the men. But the contest was unequal, for his opponent produced from his belt a short dagger with which he artfully parried two feeble blows before driving the blade home with a swift and practised gesture. The footman crumpled without a word while his conqueror, a fat man with hooded eyes, wiped the stiletto on his breeches and advanced towards us.

'Sir Richard?' Alethea took a faltering step across the tiles. Her face had gone white. But Sir Richard directed his gaze not at his shocked affianced but at me.

'Mr. Inchbold,' he said in a level tone as he removed his hat with a sweep of his arm. 'Well, well, I find I am not misinformed after all. How resourceful you must be. I saw you drown in the river with my own two eyes, though my sources insisted otherwise. I can but hope you were as resourceful in your search.' He unfastened a brass button to expose the pistol tucked in his belt. Water eddied between his boots. 'So where is it, then?' He stepped a few paces towards us. The black-clad trio at his heels eagerly followed suit. 'The Labyrinth of the World,' he said in the same even tone. 'Where is it?'

But as he took another step, reaching for his weapon, the floor of the atrium shifted like the deck of a foundering ship and the four of them lost their balance. No sooner had they righted themselves than the chandelier broke free from its mooring with a shriek and plunged to the floor, shattering into a thousand pieces between us. Sir Richard staggered backwards, still fumbling for his pistol. I felt glass skittering against my boots and then a pair of hands in the middle of my back.

'Go!' It was Alethea. 'Run!'

Chapter Nine

All four of Jupiter's moons, even Callisto, the largest, are far too dim to be sighted with the naked eye. Galileo first saw them on a winter night in January in the year 1610, using a telescope with a magnitude of 32: four moons that orbit Jupiter in periods of one and a half to sixteen and a half days. Four new worlds that no one, ancient or modern, had ever seen before. He published his discovery in Sidereus nuncius, the 'Messenger of the Stars', and within a year the sightings were confirmed by Jesuit astronomers in Rome as well as by Kepler in Prague. They were also confirmed by a German astronomer, Simon Marius, who gave the moons their names: Io, Europa, Ganymede and Callisto.

Even from the beginning the discovery provoked as much controversy as amazement. Not only were the four new satellites incompatible with the Scriptures but they also challenged Aristotle's claim in De caelo that the stars are fixed in the heavens. Worst of all, they opposed the description of the universe given in another hallowed book, Ptolemy's Almagest. Enemies of Copernicus attacked his system by arguing that if the earth is not, as Ptolemy claims, at the centre of the universe, then why should the earth, and the earth alone, possess an orbiting moon? But the revolutions of Jupiter's moons now led Galileo to recognise that the stars could orbit a planet at the same time as the planet itself orbits the sun. Jupiter and its four satellites became, for Galileo, a model for the earth and its own moon. So it was that in 1613 he wrote in the appendix to his letters on sunspots-a work opposing the Jesuit astronomer Christopher Scheiner-that the moons proved beyond all doubt the truth of Copernicanism.