Terrified, I leap back – but not before Friedrich reaches out, snatches my lantern, and hurls it at the nearby wall. It smashes upon impact, and the wooden wall, now saturated in oil, bursts into flames.

I am amazed at how quickly the fire spreads. In less than a few heartbeats it has climbed twenty feet to reach the ceiling of the corridor.

‘The Ark is on fire!’ I cry out, drawing my companions’ attention to the burning section of wall.

‘What?’ Francesca blurts, turning around to assess the situation. Then, knowing that we can no longer hold this section of the corridor, she gives one last swipe at the undead climbing the ladder, buying her the time she needs to race over to join me by the ascending ladder. ‘Armand! Blodklutt! We need to move out of this area,’ she calls out. ‘This wood is ancient and dry. It will go up in no time at all. Our only chance is to climb to the highest level of the Ark and pray that the fire doesn’t reach us. So move – before it’s too late.’

Heeding her call, Armand and Blodklutt abandon their position and sprint for the ascending ladder. Having used my remaining firearm, I watch Francesca cover their retreat with her repeating crossbow. She takes out the remaining undead coming down the corridor, and forces the Watcher – several bolts lodged in its chest – to retreat into the darkness beyond the light of our lanterns and the flames. But just as the Hexenjäger reach the ladder Friedrich Geist lurches to his feet, draws a stiletto from his belt, and lunges at Armand.

Weaving beneath the blade, Armand responds with a lightning-fast slash with one of his sabres. Caught off-guard by the speed of the attack, Friedrich staggers back, his belly sliced open by the Frenchman’s sword. Determined to end this fight quickly, Armand delivers a savage kick to Friedrich’s chest, sending him into the section of the corridor that is now ablaze.

Hoping that this is the last we will see of Friedrich Geist, Francesca, Blodklutt and I climb the ladder to the upper level. But halfway up, our eyes lock on the figure that has just climbed up from the deck below.

I give a cry of alarm, alerting Armand – who had just sheathed his sabres and is about to follow us – to the new danger. Stepping away from the ladder, the Frenchman draws his blades in preparation to face Diego Alvarez.

Although raised from the dead, Diego has not lost his knowledge of swordplay, and he proves to be the most challenging of opponents, thrusting and riposting his way forward, his rapier transformed into a humming streak of silver. Armand retreats down the corridor, focusing on defence, his sabres swatting aside his opponent’s blade. Then, sparing a concerned glance at the fire and realising that it won’t be long before it consumes the corridor leading to the ascending ladder, he takes the offensive, pressing forward with a series of thrusts aimed at Diego’s head and torso. Armand works his way past the fire and positions himself near the ladder, where he feigns to thrust at Diego’s left leg, forcing the Spaniard to block the anticipated attack. As Diego’s rapier moves down to counter Armand’s blade, the Frenchman pulls up his sword and, with a flick of his wrist, ensnares the rapier between his sabre’s extending cross-guard and its blade. Before Diego has time to pull his sword free, Armand capitalises on the advantage, lashing out with his second sabre, cleaving off Diego’s sword arm. Even before the severed limb – still holding the rapier – hits the ground, Armand whips back his first blade and drives it deep into Diego’s chest. For a second their eyes lock, and the last thing Armand sees in the Spaniard’s eyes is a burning hatred for him – a hatred that has endured even beyond death.

Rather than smile victoriously, Armand appears solemn and almost pensive as he kicks the lifeless corpse free from his blade. He stands there for a while, staring down at the lifeless Spaniard, oblivious to the fire spreading along the corridor and ignoring Francesca’s and Blodklutt’s cries that he climb up after us. Looking down at the man who has become my closest friend, only I seem to understand the significance of what the Spaniard’s death means to Armand.

There are four values that Armand holds close to his heart: his desire to defend Christ, personal honour, the bond of friendship, and the skill to wield a blade. I’m certain it is this final value that is troubling him. Although Armand is not consumed by the same fanaticism that drove Diego to challenge all swordsmen who stood in his way of becoming the greatest duellist of his age, he, too, lives by the sword.

I’m sure he is wondering how long it will be before he ends up skewered on the end of an enemy’s blade. On this occasion, Armand was yet again the victor, but those who live by the sword die by the sword, so the adage goes. Perhaps it is only a matter of time before the next duellist who deliberately baits him with personal affronts to his honour takes his life.

Francesca’s cries eventually draw Armand from his thoughts, and he sheathes his sabres and climbs after us. We are all physically drained, but the severity of our situation gives us a nervous energy. Reaching the next level, we race after Francesca, searching desperately for a means of accessing the next floor. By the time we sprint past the storeroom where I had destroyed the Tablet of Breaking, we stare back down the corridor, our attention drawn by the sound of splintering wood. The next instant, a section of the floor near the ladder collapses. Flames come roaring out of the hole, consuming the far end of the deck.

‘Let’s hope that takes care of the final Watcher and any remaining undead,’ I say, thinking that nothing could survive that furnace.

Armand clicks his tongue, and his eyes narrow sceptically. ‘Given all that we’ve been through during the last few weeks, nothing would surprise me any more.’

Spurred forward by Francesca, we continue moving down the corridor until we find a central ladder network that appears to give access to every deck of the vessel. Believing that this must have been how Friedrich Geist and Dietrich Hommel got past Blodklutt and Armand when they had been battling the undead, I follow my companions up four ladders, eventually reaching the hold.

This deck is like a warehouse, containing all of the provisions and supplies the Ark needed for its forty-day voyage. Heavy oak support beams stretch from the floor to the ceiling, and the entire deck is littered with upturned broken barrels, aged coils of rope, spare lengths of wood and threadbare cloth bags. All is coated in dust and the air has the musty smell of an ancient tomb.

‘We cannot climb any higher,’ Francesca says, moving some twenty yards into the hold before pausing to reload her crossbow. ‘Let’s just hope that the roof of the Hall of Records fully retracts, allowing the Ark to float to the surface of the Dead Sea, before the undead or the fire catches us.’

We move down to join her, when there’s a tremendous grinding noise from directly above us, like wood scraping on stone. The next instant, the Ark vibrates fiercely, forcing us to brace ourselves against the heavy wooden support beams.

‘What’s happening?’ Armand asks, terrified, his eyes locked on the upturned floor of the hold, almost as if he expects the vessel’s hull to break apart at any moment, allowing water to come gushing into the Ark.

‘The Hall of Records has flooded, and we have floated to the top of the chamber,’ Francesca says, her manner composed, as if all is going to plan. ‘That noise must be the keel – the spine of the Ark – scraping against the retracting roof of the chamber. I suggest you take a firm hold, for, once the roof withdraws, we are going to rise to the surface. It could be a rapid, turbulent ride.’

‘Let’s hope it is fast,’ Blodklutt says, gesturing with a jerk of his chin for us to look deeper into the hold, where, just at the edge of our lantern-light, smoke is wafting up through the floor. ‘The fire has been keeping pace with us. It looks as if it has already burnt its way through the floor below us.’

Sparing a worried glance over my shoulder to check if smoke is appearing elsewhere, I nearly jump out of my skin when I notice a dark, smouldering figure with one blood-red eye climb the ladder into the hold, a broad blade with glowing symbols gripped fiercely in its hands.