It drifted in like a tide, in silence. I never saw it coming. At dawn I awoke from one dream world only to be seized in the grey and damp grip of another. No caffeine ritual could dispel the effect of this fog; only wind or a searing sun. Or a hike.

The steep and narrow snake known as Marsh Creek Road between Brentwood and Mt. Diablo does wonders for a motorist’s attention to the task at hand, even in clear air. In fog, the task is tinged with the flavor of fear. Headlights that materialize a mere 40 yards away are powerful deterrents to iPhone/Starbuck’s multitasking. If you’re not alert to the present, your future could be brief. As Steven Wright put it, if everything’s coming your way, you’re in the wrong lane.

It was Saturday, Jan. 29. As my car plowed the opaque morning moisture on its way to the mountain, I wondered how my journey on Diablo’s trails would resemble my journey to the trailhead. A hike in the fog can be an exercise in aesthetic awe – or just exercise. When you can’t see more than 40 yards in any direction, the assault of a 4,000-foot peak is the scenic equivalent of a traipse down your neighborhood sidewalk.

As I motored up into Clayton, the fog’s underbelly began to lift, revealing the wizened face of North Peak, its apex still shrouded in mist. A minute later the 1,400-foot knob of Meridian Point came into view, barely beneath the bottom of the fog bank. In the foreground, Donner Canyon’s oak-clad contours lay half-cloaked in a gossamer veil.

I struck out south into Donner Canyon and swung up Meridian Ridge toward the 3,000-foot crest of Bald Ridge, where I’d take stock of the atmosphere and head up to the Summit or back down by way of North Peak. No need to haul butt to a pinnacle that provides only a sea-level vista.

For all its palpable mystery and peril, fog is a form of optical illusion. You know how it goes: the fog ahead seems blindingly solid. But with each step through it, you’re able to resolve nearby images with surprising clarity. You’re trapped in a bubble of the present; your future is hidden. There is no then; only the now.

As I climbed the narrow spine of Meridian Ridge, the canyons called Donner and Back Creek to my left and right faded into haze below. Above, the fog thinned and Bald Ridge came into focus. Suddenly I was transported from the now of nearby images to the then of a smoky height – an object one mile, one thousand feet of elevation and one-half hour in my future. Tendrils of fog lacing the ridge’s northern face like steam from a kettle swirled and coalesced into waves. A northeast breeze drove the waves up to the crest, where they collided with a southwest wind streaming in from the ocean and shattered like breakers against coastal cliffs.

Just as suddenly a tsunami of fog washed over the ridge and the vision vanished. I was alone again in the company of objects small and nearby – sage and chamise, clusters of bell-shaped blossoms dotting manzanita branches like snow – objects I could reach out and touch, objects whose scent I could catch if I paused long enough to accept the gift of the fog: the eternal here and now.

I never made it to the mountaintop. Brief glances through gashes in the ashen gauze crystallized the fact that no grand vistas would be commandeered today. Ransome Point, 400 feet beneath the Summit, was smothered. North Peak was nowhere. I was condemned to embrace the proximate and the present – a fitting sentence for one who spends an alarming share of his energy inhabiting an imagined future. I mark my calendar, set my alarm and turn my gaze upward and outward, confident the river of time will deliver me to my destination, if not my destiny.

On my traverse down North Peak I came across a boulder robed in mosses of dense and deep green flecked with tiny ferns. What archipelagos, I wondered, what continents, what worlds of strange and tireless life grace the boulders of this one mountain in Northern California? There isn’t enough time in the lifespan of our universe to exhaust the marvels of this one place. There isn’t enough future, I thought – and caught myself straining once again to imagine an existence on the far side of the fog. No, it was more than enough to have seen less than enough.

Farther down the mountain I crossed paths with a pair of hikers on the way up. It was their first time on these trails and they were lost, oblivious of the rough road ahead. I chimed in with factoids – distance, elevation, terrain – but recalling the mosses, reliving the vision of a vapor-wreathed ridge, I offered no advice. Despite my knowledge of precisely where I stood and where I was going, I was lost, too.

“You won’t see anything from the peak past 40 yards,” I told the lead hiker.

“That’s OK. It’s a good day to be out here,” she said. “Knowing where you’re going takes all the mystery out of life.”

I pinched the brim of my hat, they waved, and the three of us disappeared into the mist.