Vilém was shaking his head morosely as they swayed from side to side with the motions of the barge. It made no sense. Why should Sir Ambrose have been so intent on smuggling The Labyrinth of the World out of Prague? Sir Ambrose, a good Protestant, certainly knew the work of Casaubon. And why, too, if it was a fake, should the Cardinal wish to suppress it? Because that was who had pursued them from Prague, Vilém now told her: the agents of Cardinal Baronius.

'Can it not be opened?' Emilia, too, had returned her gaze to the cabinet. 'Is there a key for the lock?'

He shook his head again. 'Only the one kept by Sir Ambrose. I know of no other.'

The barge had now reached the deep waters and rushing currents of Woolwich. The skeletal frames of the Navy's half-finished men-o'-war could be seen in the dry-docks slipping past on the larboard side. Emilia had shifted to the opposite side of the barge, from where she could watch the waters behind them. Figures with flares and lanterns were moving back and forth in the yard entrances and among the wooden cranes whose profiles reared against the sky. As they shunted astern she thought she caught sight of another barge in the brief funnels of light, or rather a glimpse of a canvas tilt beneath which other figures could be seen. About a hundred yards of water separated them. She thrust her head out from under the awning.

'How much further before Billingsgate?'

The barge-master plunged his pole into the water, leaned on it, then raised it hand over hand. 'Eight miles or so,' he grunted before plunging it again. The boat yawed to starboard and he very nearly lost his balance. 'Two more hours,' he added after a moment. 'And that's if the tide doesn't turn.'

Emilia retreated under the awning and peered at the waters ahead. The ox-bow of the next reach with its dangerous currents lay before them. The Greenwich Marshes looked desolate, but moored along the other bank were a half-dozen Indiamen, the lanterns on their taffrails lighting thickets of masts swaying overhead. Behind them lay the East India Company's storehouses. As the barge approached the wharves, moving south now, Emilia turned her head to see the boat behind them lit by a ship's lantern. It had gained several lengths, perhaps more, since Woolwich. Two watermen were perched in the stern, while their passengers-a trio of shadowy figures-were huddled under the tilt. When she turned to Vilém she saw that he was holding something in his palm.

'Take one.'

'What?'

'It's them,' he whispered. 'The Cardinal's men.' He extended his hand a few inches. 'Eight miles. We won't make it…'

One of the East India warehouses loomed to starboard, its smell of molasses carried to them by the stiffening breeze. In its brief light she could see what he was holding: the leather pouch given to him by Sir Ambrose. Strychnos nux vomitica. Instinctively she shrank against the canvas.

'And as for the casket…' The light slid away and they were in darkness. A gull screeched overhead as he stooped, still clutching the pouch, and then raised the casket to his lap with a soft grunt. 'It will have to go overboard, I fear. Those are the instructions.'

'Whose instructions?'

No answer. He was staring fixedly at the chest. She glanced up. More wharves crowded the banks and mazes of buildings pressed up behind them. The boat slewed sideways and a wave broke over the bows, showering her cheeks and soaking her petticoats. They had gained speed but lost control in the treacherous current. The barge-master cursed and struggled to keep the vessel on a steady course, using the pole as a rudder. Their own wake overcame them as they slowed, and the barge weltered even more. After a moment the current slackened and the waterman wearily began poling again. But their pursuers had gained another few lengths.

The next hour passed with Emilia perched on the edge of the thwart, swivelling to look astern first and then at the waters ahead. Another sharp ox-bow untwisted before them at Greenwich, along with more fierce currents that set the barge moving from side to side and the barge-master cursing all over again. The sky flushed with a few hints of pink and orange and the tide slowed. Soon the river began to fill with traffic, with dozens of lighters fighting their way to the Legal Quays below the Tower, and with eel-ships and oyster-boats on their way to Billingsgate. Armadas of shallops and pinnaces dodged and feinted among them, sweeping downstream with their sails puffed. Their pursuers closed the gap but then receded after Shadwell as they were slowed in the Lower Pool by the traffic swirling about like flocks of angry birds.

A few minutes later, straining her eyes, Emilia saw the arches of London Bridge girdling the river. When she turned round she saw the tilt-boat breaking into view again. The barge-master pushed hard, dripping with sweat, but it was no use. When they finally drew even with the crowded quays in front of the custom-house, the boat was only two lengths behind. The Cardinal's men had crawled from under the tilt, and in the awakening sunlight she could see their tanned brows, their jet-black livery with its stripes of gold. All three wore lace ruffs, and one of them-the man crouched over the prow-was clutching a dagger. When she turned to Vilém he was kneeling on the floor of the barge with the casket in his hands.

'Too late…' He was crawling out from under the tilt and into the bows, where he struggled to raise the casket to the gunwales. 'We won't reach York House,' he grunted. 'We won't even reach Billingsgate!'

'No!'

Emilia clambered over the thwarts, barking her shins, then caught him in a clumsy embrace and laid a hand on the casket, before he pushed her backwards. He hoisted the cargo and once more leant over the gunwales with the treasure outstretched in his hands.

Emilia picked herself up from the boards, but at that moment the barge was bumped in the stern by the tilt-boat. She heard the master curse as the barge slewed sideways and then an instant later broadsided an oncoming skiff. The collision was violent. The last thing she saw as she was thrown to the deck was a pair of boots disappearing over the gunwales.

'Vilém!'

The barge was rocking wildly from side to side by the time she raised herself. They had been boarded. She heard, rather than saw, two of the Cardinal's men scuffling with the barge-master. The poor old devil defended himself valiantly with his pole before the dagger slit his leather jerkin, then his belly. He sank to his knees with a last oath and then tumbled over the stern as the barge was struck again, this time on the starboard quarter by a fishing smack knocked off course by the careering skiff. The Cardinal's men tumbled into one another's arms before sprawling full-length in the stern. The knife clattered to the boards.

'Emilia!'

The smack was floating past, drifting upstream with its sail flapping, while the mast crazily pendulated and the master fought hard to keep his balance in the stern. Emilia caught a glimpse of Vilém prone on the teetering deck, tangled in nets and half-buried in an avalanche of silvery fish.

'Emilia! Jump!'

The smack was moving more quickly now, skimming past the floundering barge as the wind caught in her half-furled bunts. She stepped hurriedly on to one of the rocking thwarts and was bracing herself to leap, when a hand on her skirts tugged her backwards. But at that point the barge was rammed by the fourth and last boat, a wherry filled with a dozen passengers. Then the hand disappeared and she found herself plunging towards the smack through five feet of spray and air.