Mungojerrie stood on the second step, peering down the concrete stairwell, sniffing the air, ears pricked. Then he descended.

Sasha followed the cat.

The stairs were wide enough for two people to walk abreast, with room to spare, and I stayed at Sasha’s side, relieved to be sharing the point-position risk with her. Roosevelt followed, then Doogie with the Uzi. Bobby was our tail gunner, keeping his back to one wall, crabbing sideways down the stairs, to make sure no one crept in behind us.

Aside from being suspiciously clean, the first flight of steps was as it had been on my previous visit. Bare concrete on all sides. Evenly spaced core holes in the ceiling, which had once been the end points of electrical chaseways. Painted iron pipe attached to one wall, as a handrail. The air was cold, thick, redolent with the scent of lime that leached from the concrete.

When we reached the landing and turned toward the second flight, I put one hand on Sasha’s arm, halting her, and to our feline scout I whispered, “Whoa, cat.”

Mungojerrie halted four steps into the next flight and, with an expectant expression, looked up at us.

The ceiling ahead was fitted with fluorescent fixtures. Because these lights weren’t switched on, they posed no danger to me.

But they hadn’t been here before. They had been torn out and carted away when Fort Wyvern shut down. In fact, this particular structure might have been scoured to the bare concrete long before the base was closed, when the Mystery Train ran off the tracks and scared its designers into the realization that their project had been pursued with a truly loco motive.

Time past and time present existed here simultaneously, and our future was here, too, though we could not see it. All time, said the poet T. S. Eliot, is eternally present, leading inexorably to an end that we believe results from our actions but over which our control is mere illusion.

At the moment, that bit of Eliot was too bleak for me. While I studied the fluorescent lights, trying to imagine what might wait ahead of us, I mentally recited the initial couplet of the first-ever poetry about Winnie-the-Pooh—“A bear, however hard he tries / Grows tubby without exercise”—but A. A. Milne failed to drive Eliot from my mind.

We could no more retreat from the dangers below, from this eerie confusion of past and present, than I could return to my childhood. Nevertheless, how lovely it would be to crawl under the covers with my own Pooh and Tigger, and pretend that the three of us would be friends, still, when I was a hundred and Pooh was ninety-nine.

“Okay,” I told Mungojerrie, and we continued our descent.

When we reached the next landing, which was at the doorway to the first of the three subterranean levels, Bobby whispered, “Bro.”

I looked back. The fluorescent-light fixtures above the steps behind us had vanished. The concrete ceiling featured only cored holes from which the fixtures and the wiring had been stripped.

Time present was again more present than time past, at least for the moment.

Scowling, Doogie murmured, “Give me Colombia anytime.”

“Or Calcutta,” Sasha said.

On behalf of Mungojerrie, Roosevelt said, “Got to hurry. Going to be blood if we don’t hurry.”

Led by the fearless cat, we slowly descended four more flights, to the third and final level beneath the hangar.

We found no additional indications of hobgoblins or bugaboos until we reached the bottom of the stairwell. As Mungojerrie was about to lead us into the outer corridor that encircles this entire oval-shaped level of the building, the muddy red light that we had first seen on the ground floor of the hangar pulsed beyond the doorway. It lasted only an instant and then was replaced by darkness.

A general dismay rose from our little group, mostly expressed in whispered expletives, and the cat hissed.

Other voices echoed from somewhere in this sub-subbasement, deep and distorted. They were like the voices on a tape played at too slow a speed.

Sasha and Roosevelt switched off their flashlights, leaving us in gloom.

Beyond the doorway, the bloody glow pulsed again, and then several more times, like the revolving emergency beacon on a police cruiser. Each pulse was longer than the one before it, until the darkness in the hallway retreated entirely and the eerie luminosity finally held fast.

The voices were growing louder. They were still distorted, but almost intelligible.

Curiously, not one scintilla of the malign red light in the corridor penetrated to the space at the bottom of the stairs, where we huddled together. The doorway appeared to be a portal between two realities: utter darkness on this side, the red world on the other side. The line of bloody light along the floor, at the threshold, was as sharp as a knife edge.

As in the hangar upstairs, this radiance brightened the space it filled but did little to illuminate what it touched: a murky light, alive with phantom shapes and movement that could be detected only from the corner of the eye, creating more mysteries than it resolved.

Three tall figures passed the doorway, darker maroon shapes in the red light, perhaps men but possibly something even worse. As these individuals crossed our line of sight, the voices grew louder and less distorted, then faded as the figures moved out of view along the hall.

Mungojerrie padded through the doorway.

I expected him to flare as if sizzled by a death ray, leaving no trace behind except the stink of scorched fur. Instead, he became a small maroon shape, elongated, distorted, not easily identifiable as a cat even though you could tell that he had four feet, a tail, and attitude.

The radiance in the hall began to pulse, now darker than blood, now red-pink, and with each cycle from dark to bright, a throbbing electronic hum swelled through the building, low and ominous. When I touched the concrete wall, it was vibrating faintly, as the steel post had vibrated in the hangar.

Abruptly, the corridor light flashed from red to white. The pulsing stopped. We were looking through the doorway at a hall blazingly revealed under fluorescent ceiling panels.

Instantaneously with the change of light, my ears popped, as if from a sudden decrease in air pressure, and a warm draft gusted into the stairwell, bringing with it a trace of the crisp ozone scent that lingers on a rainy night in the wake of lightning.

Mr. Mungojerrie was in the corridor, no longer a maroon blur, gazing at something off to the right. He was standing not on bare concrete but on clean white ceramic floor tiles that had not been there before.

I peered up the dark stairs behind us, which appeared to be firmly anchored in our time, in the present rather than the past. The building was not phasing entirely in and out of the past; the phenomenon occurred in a crazy-quilt pattern.

I was tempted to sprint up the steps as fast as I could, into the hangar and from there into the night, but we were past the point of no return. We had passed it when Jimmy Wing was kidnapped and Orson disappeared. Friendship required us to venture off the map of the known world, into areas that ancient cartographers couldn’t have imagined when they had inked those words Here there be monsters.

Squinting, I withdrew my sunglasses from an inside jacket pocket and slipped them on. I had no choice but to risk letting the light bathe my face and hands, but the glare was so bright that it would have stung tears from my eyes.

When we moved cautiously into the corridor, I knew beyond doubt that we had stepped into the past, into a time when this facility had not yet been shut down, before it had been stripped of all evidence. I saw a grease-pencil scheduling chart on one wall, a bulletin board, and two wheeled carts holding peculiar instruments.

The throbbing hum had not fallen silent with the disappearance of the red light. I suspected that it was the sound of the egg room in full operation. It seemed to pierce my eardrums, penetrate my skull, and vibrate directly against the surface of my brain.

Metal doors had appeared on the previously doorless rooms that opened off the inner wall of the curving hallway, and the nearest of these was wide open. In the small chamber beyond, two swivel chairs were unoccupied in front of a complex control board, not unlike the mixing board that any radio-station engineer uses. On one side of this board stood a can of Pepsi and a bag of potato chips, proving that even the architects of doomsday enjoy a snack and a refreshing beverage now and then.

To the right of the stairs, sixty or eighty feet farther along the corridor, three men were moving away from us, unaware that we were behind them. One wore jeans and a white shirt, sleeves rolled up. The second was in a dark suit, and the third wore khakis and a white lab coat. They were walking close together, heads bent, as if conferring, but I couldn’t hear their voices over the pulsing electronic hum.

These were surely the three maroon figures that had passed the stairwell in the murky red light, so blurry and distorted that I had not been able to tell whether they were, in fact, human.

I glanced to the left, worrying that someone else might appear and, seeing us, raise an alarm. Currently, however, that length of the corridor was deserted.

Mungojerrie was still watching the departing trio, apparently unwilling to lead us farther until they had rounded the curve in the long racetrack-shaped corridor or entered one of the rooms. This straightaway was five hundred feet long, from curve to curve, and at least a hundred fifty feet remained ahead of the three men before they would turn out of sight.

We were dangerously exposed. We needed to retreat until the Mystery Train staffers were gone. Besides, I was already nervous about the quantity of light that was hammering my face.

I caught Sasha’s attention and gestured toward the stairwell.

Her eyes widened.

When I followed her gaze, I saw that a door blocked access to the stairs. From inside the stairwell, there had been no door; we had seen straight through to the red—and then to the fluorescent-drenched—hallway. We had passed directly from there to here without obstruction. From this side, however, the barrier existed.

I went quickly to the door, yanked it open, and almost crossed the threshold. Fortunately, I hesitated when I sensed a wrongness about the darkness beyond.

Sliding my sunglasses down my nose, peering over the frames, I expected concrete-walled gloom with steps leading up. Instead, before me was a clear night sky, necklaces of stars, and a pendant moon. This skyscape was the only thing out there where the stairs had been, as though this door now opened high above the earth’s atmosphere, in interplanetary space, a long way from the nearest doughnut shop. Or perhaps it opened into a time when the earth no longer existed. No floor lay beyond the threshold, nothing but empty space jeweled with more stars, a cold and infinite drop from the bright corridor in which I stood.

Sharky.

I closed the door. I gripped the shotgun fiercely in both hands, not because I expected to use it but because it was real, solid and unyielding, an anchor in this sea of strangeness.

Sasha was now immediately behind me.

When I turned to face her, I could tell that she had seen the same celestial panorama that had rocked me. Her gray eyes were as clear as ever, but they were darker than before.

Doogie hadn’t glimpsed the impossible sight, because he was holding the Uzi at the ready and watching the three departing men.

Frowning, standing with his fists balled tightly at his sides, Roosevelt studied the cat.

From his position, Bobby couldn’t have seen through the doorway, either, but he knew something was wrong. His face was as solemn as that of a rabbit reading a cookbook recipe for hare soup.

Mungojerrie was the only one of us who didn’t appear to be about to blow out snarled springs like an overwound cuckoo clock.

Trying not to dwell on what I’d seen beyond the stairwell door, I wondered how the cat could find Orson and the kids if they were in a present-time place while we were stuck here in the past. But then I figured that if we could pass from one time period to another, be caught up in the time shifts taking place around us, so could my four-footed brother and the children.

Anyway, from every indication, we hadn’t actually traveled back in time. Rather, the past and present—and perhaps the future—were occurring simultaneously, weirdly pressed together by whatever force or force field the engines of the egg room had generated. And perhaps it was not only one night from the past that was bleeding into our present time; maybe we were experiencing moments from different days and nights when the egg room had been in operation.

The three men were still walking away from us. Ambling. Taking their sweet time.

The rhythmic swell and recession of the electronic sound began to have an odd psychological effect. A mild vertigo overcame me, and the corridor—this entire subterranean floor—seemed to be turning like a carousel.

My grip on the shotgun was too fierce. Unwittingly, I was exerting dangerous pressure on the trigger. I hooked my finger around the trigger guard instead.

I had a headache. It wasn’t a result of being knocked around by Father Tom at the Stanwyk house. I was sustaining a brain bruise from pondering time paradoxes, from trying to make sense of what was happening. This required a talent for mathematics and theoretical physics; but although I can balance my checkbook, I haven’t inherited my mother’s love of math and science. In the most general sense, I understand the theory of leverage that explains the function of a bottle opener, why gravity makes it a bad idea to leap off a high building, and why running headlong into a brick wall will have little effect on the bricks. Otherwise, I trust the cosmos to run itself efficiently without my having to understand it, which is also pretty much my attitude toward electric razors, wristwatches, bread-baking machines, and other mechanical devices.

The only way to deal with these events was to treat them as supernatural occurrences, accept them as you might accept poltergeist phenomena—levitating chairs, hurtling knick-knacks, doors slammed by invisible presences—or the spectral appearance of a moldering and semitransparent corpse glimpsed on a midnight stroll in a graveyard. Thinking too much about time-bending force fields and time paradoxes and reality shifts, straining to grasp the logic of it, would only make me crazy, when what I desperately needed to be was cool. Calm. Therefore, this structure was just a haunted house. Our best hope of finding our way through its many rooms and back to the safer side of the spook zone was to remember that ghosts can’t hurt you unless you yourself give them the power to harm you, unless you feed their substance with your fear. This is the classic theory, well known to spirit channelers and ghostbusters all over the world. I think I read it in a comic book.

The three ghosts were just fifty feet from the turn that would finally take them out of sight, around one arc of the long racetrack corridor.

They stopped. Stood with their heads together. Talking above the throbbing noise that flooded the building.

The specter in the jeans and white shirt turned to a door and opened it.

Then the other two wraiths—the one in the suit, the one in the khakis and lab coat—continued toward the end of the hall.