He placed his left hand on one of the doorknobs, became aware of a pungent odour, paused, then twisted and pushed.

The door swung open. The explorer took two steps forward and stopped.

Laurence Oliphant halted in mid-recitation. His eyes met Burton’s. He was standing in the middle of a pentagram painted on the floor. Clouds of foul-smelling smoke billowed from small brass censers positioned at its points. William Stroyan, obviously dazed and with blood dripping from a wound on his forehead, was kneeling at Oliphant’s feet, facing away from him and toward Burton. Oliphant was gripping the lieutenant’s hair and holding a large curved knife to his throat.

He sneered and slid the blade sideways.

Burton gave a cry of horror as blood spurted and his friend collapsed to the deck.

Oliphant raised his arms into the air. His eyes blazed triumphantly. “It is done! The way is open! I await thy coming, Master! I await thy coming! Thou shalt endure until the end!”

Barely aware of his own actions, Burton lifted the swordstick and drew the blade.

“That’s my cane,” Oliphant said.

The statement, so mundane amid such extraordinary circumstances, strengthened Burton’s growing conviction that he was caught up in a fever-fuelled fantasy. He levelled the weapon at Oliphant—its tip shook wildly—and quickly glanced around, hardly comprehending what he saw. The walls of the observation room—three of glass; the fourth, at his back, of wood panels—were painted all over with squares, subdivided, each division containing a sequence of numbers. Beyond the glass, in the clear night sky, curtains of multicoloured light were materialising, shifting and folding, blocking the stars, and fast making the night as bright as day.

“Your cane?” Burton mumbled.

A horrible bubbling diverted his attention back to Stroyan. He saw the lieutenant’s life gutter and depart.

Burton’s eyes snapped up to Oliphant, who held out a hand and said, “I’ll have it, if you please. It is bespoke. The only one of its kind. I had it fashioned in memory of a white panther I once kept as a pet. Marvellous creature. Don’t you admire the single-mindedness of the predator, Captain?”

Uttering an inarticulate yell, Burton hurled himself forward, but his left knee gave way and his charge instantly became an uncoordinated floundering. He stabbed at Oliphant’s shoulder, intending a disabling wound, but his opponent slashed his knife upward and deflected the rapier, sending Burton even more off-kilter. The two men collided and crashed to the floor. They grappled, Oliphant’s weapon tangling in the explorer’s jubbah, Burton dropping the sword and seeking a stranglehold.

Oliphant cried out, “Get off me! It’s too late! It’s him you should worry about now. He knows who you are, Burton. He’ll come for you! He’ll come for you!”

Burton punched him hard on the left ear, then, as the knife came free of the cloth, caught the man’s wrist and strained to prevent the weapon from being thrust into his chest.

Who does he mean? Who’s coming for me?

Without loosening his grip, Burton jerked his arms to the side and gouged his elbow into the other’s eye.

Too fragile for this. Too damned fragile.

Oliphant twisted. The knife sliced through cloth and scraped across Burton’s ribs. The explorer yelped, rolled over until he was on top of his foe, then slammed his forehead into the man’s face, hearing the back of the other’s skull clunk loudly on the deck. Lord Elgin’s secretary went limp. Burton pushed himself up, sat on Oliphant’s stomach, and with all the strength remaining to him, sent his fist crashing across the man’s jaw. His opponent became still.

There. That’ll keep you quiet, you bastard.

Falling to the side, he flopped onto his back and blacked out.

The distant coughing of lions.

The soothing songs of his bearers as the safari settled for the night.

The jungle, as red as blood.

Red?

The Other Burton’s voice: Parallel all things are; yet many of these are askew; you are certainly I; but certainly I am not you.

“Burton! Captain Burton! Captain Burton!”

He opened his eyes and saw Nathaniel Lawless looking down at him. The airship captain’s eyes were of the palest grey, his teeth remarkably straight and white, his snowy beard tightly clipped. Second Officer Wordsworth Pryce and Doctor Quaint were standing to either side of their commander.

Burton moistened his lips with his tongue. He said, “The sky.”

“I know,” Lawless responded. “It’s the aurora borealis. But this bright and this far south? In all my days, I’ve never seen the like. Are you all right?” He stretched down a hand and helped the explorer to his feet.

“Comparatively speaking, yes.”

“You’re covered in blood.”

“Most of it is William’s. I have a scratch across the ribs, nothing more.”

Doctor Quaint interjected, “Let me see it.”

“Later, Doctor.”

Burton turned and saw that rigger Alexander Priestly and engineer James Bolling—both big, beefy men—were holding the unconscious Laurence Oliphant upright.

Lawless asked, “He killed Stroyan?”

“He did.”

“Why? And what are all these scribbles on the floor and walls?”

“It was some sort of ritual. A summoning, I think. William was the sacrifice.”

“Summoning? Summoning of what? From where?”

“I haven’t a notion.”

Burton picked up the rapier and its sheath, slid the one into the other, then supported himself on the cane and waited for his head to clear. The Saltzmann’s was causing a ringing in his ears and had put a strange glow around everything he saw. Or was that caused by the rippling illumination outside?

He took a deep breath, blinked, and addressed the second officer. “Pryce, would you mind fetching my notebook from the bureau in my quarters? I’d like to make a record of these diagrams and numbers.”

Pryce gave a nod and departed.

Lawless jerked a thumb toward Oliphant. “I suppose I should lock this lunatic in one of the cabins.”

Burton slipped his hand into his jubbah and gingerly touched the laceration running down his left side. His fingertips slid through warm wetness. He winced, and nodded. “Strap him down onto the bed. Make sure he can’t move. We’ll give him to the police when we reach London. I’ll have a word with Lord Elgin.”

“I can do that,” Lawless objected. “You should go back to bed. You look sick as a dog—your skin is jaundiced.”

“I’m over the worst of it, Captain. The excitement appears to have jolted me back to my senses. I’d rather see Elgin myself, if you don’t mind.”

“As you wish.”

A couple of minutes later, Pryce returned and handed over Burton’s notebook. Oliphant was hustled away. Quaint bandaged the explorer’s wound then summoned a couple of crewmembers and helped them carry William Stroyan’s corpse off to the ship’s surgery.

Burton pushed to the back of his mind the misery he felt at his friend’s death. He sketched. Each wall, he noted, had been divided into a seven-by-seven grid, the outer squares of which were densely filled with numbers. The next squares in—five by five—contained fewer numerals. They surrounded three by three, in each of which only four-figure numbers were painted.

Burton couldn’t work it out, but he felt sure some sort of mathematical formula was in operation, which led to what he guessed was the “sum” in the central square of each wall. Behind him, on the wood panelling, this final number was ten; on the wall to his left, eight; on the wall in front, one thousand; and on the right-hand wall, nine hundred.

He was aware of Lawless looking over his shoulder until the diagrams were copied, then the captain crossed the deck to one of the glass walls and stood beside it, gazing out at the sky. “You surely don’t expect me to believe he magicked up the aurora?”