I yanked Openshaw to one side, shouting “Get inside, man!” Edwards lay stone dead in the street, but it wasn’t revenge that made me fire, it was utter dread. The bullet hit its target – from that range, I would’ve made the shot blindfolded – but it had no effect. The apparition strode on as though it hadn’t seen me at all. I dashed inside and locked the door, trembling. The naked stranger, now jumping into a pair of my trousers he’d grabbed from the wash basket, sprinted upstairs. The constable and I followed.

“What is it?” I asked.

“A devil!” Openshaw panted. “It’s killed half a dozen people across town. We couldn’t do anything to stop it, sir. It’s like there’s nothing there to fight – nothing more than a damn shadow!”

I clutched the banister at the top of the flight and looked downstairs. The figure was in the vestibule, yet the door remained untouched. Through solid wood? It climbed the first step before I bolted for Madelaine’s room.

“What do we do now, sir?” asked Openshaw, as I barged him aside on the landing.

“We all get the hell out. Maddy!”

She flung her door open, still holding the croquet hammer she’d chosen for self-defence. I hurried her to the back bedroom, which was empty – where the stranger slid the window open.

“What is that thing, Johnny?” she asked.

“I don’t know. How long’s it been since you climbed the trellis?”

“Don’t worry about me. I’m still younger than you.”

The stranger looked round in a panic. “Trellis – where?”

“Just to the left; it’s overgrown by now,” I replied.

He didn’t pause to check. His physique belied a startling agility; before Madelaine grasped the first vine, he’d climbed the twenty feet and rolled onto the lawn like one of Sabatini’s swashbucklers. My sister found it trickier but kept her footing. The black figure suddenly entered the room behind us. I felt my chest tighten.

“Jump, constable! Jump for it!”

Openshaw landed with a cry. I thought about a running leap to reach the branches of the old chestnut tree. Too far! No time! I climbed out backwards onto the sill. Blackness enveloped the entire room; the figure was inches from my face. I dived onto the sprawling vines, ripping the trellis apart. The momentum felt like freefall, but the creepers stayed me just enough to land me on my feet. The apparition was already three steps ahead on the lawn. It veered sharply to the right, then slightly to the left. What’s it doing? I noticed the barefooted stranger zigzagging across next door’s garden. Madelaine supported Openshaw as he limped in the opposite direction. There was my answer. The black shape, whatever it was, wanted the stranger…and only the stranger.

“Constable, go back inside and telephone the station,” I said. “Have someone pick you up. Tell Farley to get in touch with Scotland Yard in Waltham. Ask for Lt. Flint. Fill him in as best you can then give my name, and tell him I’m coming to him. Got all that?”

“I think so, sir. What will you do?”

“Keep him on the move…as long as I can,” I replied.