This essay was published, in a slightly edited form, on Mr. Beller’s Neighborhood.

My father had two head-on collisions in nine months—without remembering how he’d gotten into either of them—before we could convince him to go the neurologist. Despite my suspicions, I didn’t learn it was Alzheimer’s for sure until my oldest brother called to tell me on the day before Thanksgiving. The call came ten minutes before my parents were due to arrive at my apartment for a visit, and I was still on the phone when the doorbell rang. I opened the door, gave my mother a long, sad hug, and looked past her at the empty hallway. When I asked where my father was, she told me he was parking the car.

“Oh, Jesus. Have fun!” my brother said in my ear, and hung up.

“It’s fine,” my mother whispered. “What’s the worst that could happen?”

I had no idea why she was whispering. What was clear was that, now its time had finally arrived, this family trip through the maze of Alzheimer’s was going to be weirder than I ever imagined.

For starters, my parents live in Pennsylvania, and the Department of Motor Vehicles there doesn’t consider two head-on collisions and an Alzheimer’s diagnosis sufficient reason to revoke a driver’s license. Instead, they offer three chances to pass a driving test with an evaluator specifically trained to assess Alzheimer’s patients.

“Don’t worry, Dave,” said my father’s evaluator after my father failed twice. “I know you can lick this. It’s all in your mind.” Three weeks later, I got a distraught call from my mother telling me he’d passed the third test. “Talk to him,” she said. “He’ll listen to you.”

In the summers when I was seven and eight, we went to Maine for two weeks so my father could oversee construction of a house he’d designed for a colleague. It was a twelve-hour trip, and long after the rest of the family was asleep I sat up awake with excitement while he drove. We spoke in hushed tones about the piles of lobster claws we would eat, and how funny it was that there was a big dipper in the sky, and as we flew up the highway under the canopy of silent stars I understood that we were really flying along the skin of a planet spinning its way across a universe so big you couldn’t imagine its end, and I got on the phone with my father the day he passed his third and final driver’s test at the age of 72 and convinced him to hang up his car keys for good.

I visited my parents the following June. On the first night of my visit we all went out to dinner, and my father disappeared without leaving his seat. He had a slight smile on his face, but it was the smile I know I have in a noisy bar when I can’t hear what anyone is saying and have given up trying, pretending instead to listen and hoping that eventually someone will say something I can understand. When the waitress came to the table he moved his hand uncertainly around the menu and eventually ordered grilled shrimp salad because, I suspect, it was the last as well as the first item my mother suggested. It wasn’t until later that it occurred to me his eyesight had deteriorated so much that he could barely read.

In Alzheimer’s disease, neurofibrillary tangles (which look like ropes) and beta-amyloid plaques (which look like lumps) form deposits on message receptors in the brain and disrupt the thought process. Words move around on the page. Before the end of a sentence is reached, the beginning is forgotten. One misread word can send an entire train of thought down an alternate track. Typical scenario: a patient misreads the word “accordingly” as “accordion,” then lacks the capacity to deduce the meaning contextually and the concentration to begin the sentence again. “Accordion?” goes the thought. “That doesn’t make sense. What’s an accordion doing there?”

That’s true: it doesn’t make sense. And therein lies the oddness of this disease, its strange and sometimes strangely poetic moments. Words are sometimes substituted not because they have a similar meaning, but because they look the same on the page or share key sounds. Referring to a mountain cottage my grandfather built, my father called it a cabbage. I don’t know how much of his difficulty with the menu was due to failing eyesight; it may simply be that his hours of clarity are becoming abbreviated, like the span of sunlight in a polar winter. I do know that in the same way he’s losing language, I’m losing him. The shape of the man with the menu was that of the man I understand to be my father, but the meaning had gone all awry.

As I drove my parents home from the restaurant, a car the color of yellow road paint started through a four-way stop sign out of turn and came at us from the left. It was moving slowly and stopped promptly, but I reacted like a dyed-in-the-wool New Yorker.

“Hey, not your turn, dickhead!” I called out.

I’d like to point out here that after eight years of living in New York, yelling things like this isn’t really hostile, per se: the general tone was similar to what it would be if you chucked someone affectionately on the shoulder and called them a chump. Still, I cringed when I heard the words fly out of my mouth. Who on earth would my parents think I’d become? They sat silently in their WASPy spring outfits, my father in a blue seersucker suit and a bow tie, my mother in summer weight beige wool and a smattering of gold jewelry. Mahler’s Fifth Symphony floated quietly up from the radio.

Then, from the backseat: “Yeah, dickhead!” said my mom.

“Hey, dickhead,” my dad chimed in from the passenger seat. “Hey fuck you, dickhead!”

“Yo, you’re a dickhead!” my mother yelled, collapsing with laughter.

No family journey is without its collisions; our own is littered with the detritus of multiple three-way pileups, the jagged refuse of years spent screaming around the same corner from different directions and discovering too late that none of our brakes had been properly fixed. But as the yellow car faded into the distance, I realized nothing is going to get us through this longest, strangest trip of them all like being the kind of family that can lean out a car window and yell, “Hey dickhead!” together.

Nothing.