But enter I did, because that’s where the girl’s footprints led. Inside, the cairn tunnel was damp and narrow and profoundly dark, so cramped that I could only move forward in a kind of hunchbacked crab-walk. Luckily, enclosed spaces were not one of the many things that scared the hell out of me.

Imagining the girl frightened and trembling somewhere up ahead, I talked to her as I went along, doing my best to reassure her that I meant no harm. My words came slapping back at me in a disorienting echo. Just as my thighs were starting to ache from the bizarre posture I’d been forced to adopt, the tunnel widened into a chamber, pitch black but big enough that I could stand and stretch my arms to either side without touching a wall.

I pulled out my phone and once more pressed it into service as a makeshift flashlight. It didn’t take long to size up the place. It was a simple stone-walled chamber about as large as my bedroom—and it was completely empty. There was no girl to be found.

I was standing there trying to figure out how the hell she’d managed to slip by when something occurred to me—something so obvious that I felt like a fool for having taken this long to realize it. There never was any girl. I’d imagined her, and the rest of them, too. My brain had conjured them up at the very moment I was looking at their pictures. And the sudden, strange darkness that had preceded their arrival? A blackout.

It was impossible, anyway; those kids had all died a lifetime ago. Even if they hadn’t, it was ridiculous to believe they would still look exactly as they had when the photos were taken. Everything had happened so quickly, though, I never had a chance to stop and wonder if I might be chasing a hallucination.

I could already predict Dr. Golan’s explanation: That house is such an emotionally loaded place for you, just being inside was enough to trigger a stress reaction. Yeah, he was a psychobabble-spewing prick. But that didn’t make him wrong.

I turned back, humiliated. Rather than crab-walking, I let go of the last of my dignity and just crawled on my hands and knees toward the gauzy light coming from the mouth of the tunnel. Looking up, I realized I’d seen this view before: in a photograph in Martin’s museum of the place where they’d discovered the bog boy. It was baffling to think that people had once believed this foul-smelling wasteland was a gateway to heaven—and believed it with such conviction that a kid my age was willing to give up his life to get there. What a sad, stupid waste.

I decided then that I wanted to go home. I didn’t care about the photos in the basement, and I was sick of riddles and mysteries and last words. Indulging my grandfather’s obsession with them had made me worse, not better. It was time to let go.

I unfolded myself from the cramped cairn tunnel and stepped outside only to be blinded by light. Shielding my eyes, I squinted through split fingers at a world I hardly recognized. It was the same bog and the same path and the same everything as before, but for the first time since my arrival it was bathed in cheery yellow sunlight, the sky a candy blue, no trace of the twisting fog that, for me, had come to define this part of the island. It was warm, too, more like the dog days of summer than the breezy beginnings of it. God, the weather changes fast around here, I thought.

I slogged back to the path, trying to ignore the skin-crawly feeling of bog-mud gooshing into my socks, and headed for town. Strangely, the path wasn’t muddy at all—as if it had dried out in just a few minutes—but it had been carpet-bombed with so many grapefruit-size animal turds that I couldn’t walk in a straight line. How had I not noticed this earlier? Had I been in some kind of psychotic haze all morning? Was I in one now?

I didn’t look up from the turdy checkerboard that stretched out before me until I’d crossed the ridge and was coming back into town, which is when I realized where all the mess had come from. Where this morning a battalion of tractors had plied the gravel paths, hauling carts loaded with fish and peat-bricks up and down from the harbor, now those carts were being pulled by horses and mules. The clip-clop of hooves had replaced the growl of engines.

Missing, too, was the ever-present buzz of diesel generators. Had the island run out of gas in the few hours I’d been gone? And where had the townspeople been hiding all these big animals?

Also, why was everyone looking at me? Every person I passed stared at me goggle-eyed, stopping whatever they were doing to rubberneck as I walked by. I must look as crazy as I feel, I thought, glancing down to see that I was covered in mud from the waist down and plaster from the waist up, so I ducked my head and walked as fast as I could toward the pub, where at least I could hide in the anonymous gloom until Dad came back for lunch. I decided that when he did, I would tell him straight out that I wanted to go home as soon as possible. If he hesitated, I would admit that I’d been hallucinating, and we’d be on the next ferry, guaranteed.

Inside the Hole were the usual collection of inebriated men bent over foamy pint glasses and the battered tables and dingy decor I’d come to know as my home away from home. But as I headed for the staircase I heard an unfamiliar voice bark, “Where d’ya think yer going?”

I turned, one foot on the bottom step, to see the bartender looking me up and down. Only it wasn’t Kev, but a scowling bullet-headed man I didn’t recognize. He wore a bartender’s apron and had a bushy unibrow and a caterpillar mustache that made his face look striped.

I might’ve said, I’m going upstairs to pack my suitcase, and if my dad still won’t take me home I’m going to fake a seizure, but instead I answered, “Just up to my room,” which came out sounding more like a question than a statement of fact.

“That so?” he said, clapping down the glass he’d been filling. “This look like a hotel to you?”

Wooden creaks as patrons swiveled around in their stools to get a look at me. I quickly scanned their faces. Not one of them was familiar.

I’m having a psychotic episode, I thought. Right now. This is what a psychotic episode feels like. Only it didn’t feel like anything. I wasn’t seeing lightning bolts or having palm sweats. It was more like the world was going crazy, not me.

I told the bartender that there had obviously been some mistake. “My dad and I have the upstairs rooms,” I said. “Look, I’ve got the key,” and I produced it from my pocket as evidence.

“Lemme see that,” he said, leaning over the counter to snatch it out of my hand. He held it up to the dingy light, eyeing it like a jeweler. “This ain’t our key,” he growled, then slipped it into his own pocket. “Now tell me what you really want up there—and this time, don’t lie!”