She made a polite huh noise. Nice way to keep a conversation going, Vicky. Now she thinks you kill bugs for a living. Not a topic for a chat—unless she had cockroaches in her kitchen, which probably wasn’t something she’d care to think about while eating.

God, I’d be hallucinating in a minute.

Then her eyes widened. “Demons! You exterminate demons, don’t you?” She sat up straight, rattling the dishes on her tray. “That’s why you look familiar! I saw you on CNN a couple of months ago.”

Not that again. Wouldn’t that story ever dry up and blow away?

“I’m an amateur demonologist myself,” she was saying. From there, she launched into a detailed explanation of her research with all the hyped-up enthusiasm of a hobbyist with a captive audience. I smiled and nodded and couldn’t get a word in edgewise.

She kept going for most of an hour. I don’t know how she could talk so long without pausing for breath. She gave her opinion about Russom’s (terribly in need of updating) and whether incubi and succubae were more properly classified as soul suckers or energy vampires. But she really got passionate when she launched into her issues with how the Library of Congress catalogs demonology books. “You can find them in BF 1501 to BF 1562, which is the sub-subclass for Demonology, Satanism, and Possession. Makes sense, right? I mean, that’s where anyone would look for them first. But then there’s BT 975, Invisible Worlds, which includes some books about demons. And don’t even get me started about the GR subclass. That’s folklore. Folklore! Even though people like you have proved beyond any doubt that demons are real. But no. You’ll find still demonology books shelved in the Folklore section, GR 500 to GR 615 …” It was hard to share her sense of outrage when my eyelids kept sliding shut.

Eventually, she yawned. “This has been fascinating. I’m so thrilled to have met you. But I’d better get some sleep. I’ve got a late-morning meeting in London.” She laid her seat out completely flat, pulled a blanket over herself, put on a sleeping mask, and was gently snoring within a couple of minutes.

So unfair. The only time I’ve ever crossed the Atlantic in a seat that turns into a bed, and I couldn’t try it out.

I got up to use the can’t-turn-around-in-it bathroom. It felt good to move around, so I walked up and down the aisle to stretch my legs. But the combination of caffeine-jittery and utterly exhausted didn’t keep me steady on my feet. The second time I lurched sideways into a sleeping passenger, a flight attendant came over and touched my arm.

“I’m afraid you’re disturbing other passengers,” she said in a low voice, ushering me along. “Could you please return to your seat?”

“Sorry,” I muttered. “I can’t sleep.”

“Can I get you some chamomile tea? That always helps me nod off.” We arrived at my seat. “Let me help you make up your bed.”

“No, you don’t understand. I can’t sleep.” As in If I fall asleep, I’ll invite a Hellion onto the plane.

She tilted her head, waiting for me to explain.

“Just bring me another cup of coffee, please.” I sat down, rubbed my sand-filled eyes, and waited for the miles to pass.

WE ARRIVED IN LONDON AT SEVEN IN THE MORNING. THE sky was thick with clouds—lots of bumps during the descent. The temperature was warmer than in Boston, but the dampness made it feel almost as cold.

Before we deplaned, the amateur demonologist librarian asked for my card. When I told her I didn’t have one, she gave me hers. I stuck it in my back pocket. If I ever hear of a demonologists’ conference, maybe I’ll give her a call.

Somehow I made it through customs, changed some money, and snagged a cab. Heathrow is in a western suburb of London, and I had to get to Euston Station in the northern part of the city. In the taxi, I tried not to let my head loll back on the seat, making myself sit upright and watching buildings blur past. Little sparkles shimmered across my vision. I blinked, trying to clear them, then gave up and watched the light show.

At Euston, I bought a one-way ticket to Rhydgoch, Wales. The agent handed me three tickets: Euston Station to Chester, Chester to Wrexham, and then the little puff-puff local to Rhydgoch. Two changes—not bad for the trek to my aunt’s remote village.

I bought a phone card and found a bank of phones. There, I made a quick call to the Cross and Crow and left a message in case Mab or Jenkins came in, letting them know the time of my train. I talked to someone named Anna, who said she was the day cleaner and seemed annoyed I was asking her to play secretary. I’d rather have spoken to Mr. or Mrs. Cadogan; they knew me and would make sure Mab got the info one way or another. But it was okay. Once I made it to Rhydgoch, I’d be on familiar turf.

But first I had to get there. I stopped in a newsagent’s and bought the thickest magazine I could find, then made my way across the concourse, past kiosks and coffee stands, dodging briefcase-toting, rush hour-crazed commuters determined to mow down anything in their path. I double-checked the large electronic boards for my train, found the platform, and walked, oh, five hundred or so miles along that platform until I reached the right car. Clutching the railing, I heaved myself up the steep steps onto the train. I staggered a bit as I walked along the aisle in search of my seat, and my head spun with the effort of lifting my duffel onto the luggage rack. At last, I could plop down into my seat.

All that effort left my heart pounding as though I’d sprinted across London. I was moving into that stage of exhaustion where every little motion wrings you out. Just as well. With my heart racing the way it was, I wouldn’t fall asleep anytime soon.

Whistles blew, doors closed, and the train lurched forward. We rolled out of the station into the thin winter daylight, past soot-stained, graffiti-covered brick walls, then the backs of tiny, run-down row houses with graying net curtains at the windows. London. It felt unreal to be here. I could almost believe I was dreaming—all I needed was to have Difethwr pop up and wave to me from someone’s back garden.

After a few minutes of watching buildings go by, I pulled out my magazine and opened it to a random page. Hostile-looking models with pointy chins and even pointier elbows wore dresses that looked like burlap sacks with ruffles. So not my style. Another fashion spread showed models in gray-green makeup posing stiffly in torn gowns. Zombie chic. Tina would love it. Maybe she’d take up modeling next.

The train picked up speed as we moved beyond the city, and I gazed out the window, feeling dizzy as suburban London houses gave way to fields and villages. An attendant wheeled a snack trolley down the aisle. I bought another cup of coffee but passed on the plastic-wrapped sandwiches and muffins. Hang on, Vicky. I sipped the hot, bitter drink. You’re almost there, only six hours, two train changes, and a dozen more cups of coffee to go.

Trying to shake off the heaviness, I wiggled my shoulders, crossed my legs one way, and then crossed them the other way. I stood up, stretched, walked to the end of the car, stretched again, came back, sat down. Eventually, I went back to flipping magazine pages. When I saw a familiar face smiling at me from a moody black-and-white photograph, I blinked—twice—thinking maybe I’d finally started hallucinating. But no, there was Mr. Cadogan, his sleeves rolled up, leaning over the bar at the Cross and Crow and looking serious, despite the characteristic twinkle in his eye. The caption read, “Lloyd Cadogan owns the Cross and Crow, in the Welsh village of Rhydgoch, whose resident ghost is nicknamed ‘Spooky Lil.’ ” Below the photo of Mr. Cadogan was another black-and-white shot of the pub’s interior, showing a blurry column of mist in front of the massive old fireplace. For this photo, the caption asked, “Fact or figment: Does ‘Spooky Lil’ haunt the site of her centuries-old murder?”

I turned back the page to find the name of the article: “Britain’s Most Haunted Pubs.” Half a dozen pubs were featured; I skimmed until I found the part about the Cross and Crow. I’d known Mr. Cadogan since I was a little girl, so the story of Spooky Lil was a familiar one. According to legend—or at least the legend dreamed up by Mr. Cadogan—Lil was an eighteenth-century barmaid who’d gotten pregnant by the local squire’s son. When the boy wanted to marry Lil, his enraged father ordered his henchmen to get rid of the problem. They’d strangled Lil and buried her body in the cellar. Ever since, Spooky Lil had haunted the pub, moaning for her lost love.

Even though Mr. Cadogan swore Lil was real, his tragic tale of a strangled barmaid was a ploy to draw in tourists. The Cross and Crow had half a dozen rooms for rent, and Mr. Cadogan could charge double the usual rate for the haunted bedroom—somehow, the bedroom that was “haunted” always seemed to be the highest-priced room available. Nothing like sleeping in a haunted bedroom for a good, safe thrill. Maybe that was because so many real monsters had come out into the open in the past few years that norms preferred their close encounters to be of the make-believe kind.

Norm psychology. Who could tell?

The haunted pubs article kept me diverted until it was time to change trains in Chester. For the rest of the trip, time lost all meaning and everything went by in a blur. I’d long ago grown used to the itchy eyes; the sparkly, bleary, wavy vision; the feeling of moving underwater. I was sick with tiredness, but I could deal with that, too. I was getting there. I switched trains again in Wrexham. Wales, I thought, looking around. I’ve made it to Wales.

When the slow-moving local train finally pulled into Rhydgoch station, brakes screeching, I wanted to sing with triumph. There it was: the sooty, one-story, redbrick building, the crooked RHYDGOCH sign. If this were summer, there’d be hanging baskets overflowing with red and white flowers. But it was late January, and the only decoration was a dusting of snow on the station roof.

Several people waited on the platform, scanning the train’s windows. I didn’t see Mab or Jenkins, but they might be in the car park. Or maybe they hadn’t gotten my message. No problem. I knew where I was now.

Eager to get off the train, I stood. The car seemed to slide away from me, and I had to grab the back of the seat in front of me to steady myself. My ears rang, and I was sweating despite the cold air pouring in through the open door. I’d gone so far beyond tired that tired would feel refreshing. But I was almost there. Almost safe. When I got to Maenllyd, Mab would take away the burden I’d been carrying since Difethwr had entered my dreamscape. I didn’t know how, but I trusted that she would.