Before we could convince him to go the neurologist, my father had two head-on collisions in eleven months without remembering how he’d gotten into either of them. 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.

My brother said, “Oh, Jesus,” 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, now that 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. They live just outside Philadelphia in a former carriage house situated halfway down the hillside of a lush, miniature valley. The triangular grassy plateau on which it sits rises up from the sloping ground and points toward the basin of the valley like the prow of a ship, and the springtime sun sets off an explosion of fragrant color against its whitewashed walls. The house is about a mile from the small business district on top of the hill. My father is a de facto prisoner in this little paradise, but he likes to work in the yard. Once, he started walking to the hardware store to buy a new trowel. Halfway there, he discovered he had forgotten his wallet and had to walk back to get it. A trip that would have taken twenty minutes in a car took him an hour and a half on foot; by the time he got back to the house, he was too exhausted to do anything but take a nap.

On the first night of my visit we went to dinner at a restaurant 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 so deteriorated 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 often 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 Norwegian 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 is 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 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 was 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, I thought, as the yellow car faded into the distance, 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.