THE eldest, on final countdown to an early morning dash to Dublin Airport to return to a year away in California, is arguing the finer points of some useless trivia with the younger middle teen, as I stand staring off into space, elbow-deep in what was supposed to be an avocado dip.
The pair have gone from 'yes it is'/'no it's not' ping-pong to briefly staring each other out, then frantically digging for iPhones in a race to fact-check whatever it is, I don't even know what - earlier it was seagulls having no rectums, now I think I've heard something about 'hoverboards'.
It is, in fact, all more than a bit Back to the Future, this déjà-vu of having the eldest home for a few short weeks and only just returning to the normality of the rather abnormal family I think we are, mere hours before he leaves again for his own time zone, eight hours behind, on the other side of the world.
I shoot a glance at the clock, checking the time left before we've to fall out of bed and haul bags to the car... and the Christmas holidays will well and truly be over.
I give up on the dip, wiping my hands on a towel and observing our family. It's a very fragile snapshot we inhabit, I decide, six of us about to sit down to dinner together for the last time in six months. In a matter of hours, this will all be a memory and I suddenly wish that time would stand still.
"I'm telling you," says one of the boys. "Seriously," says the other, "you're wrong." The point is poked into submission on touch-screens. "Damn," mutters the eldest. "Knew it," grins his brother.
We all repair to the table to eat and I notice what easy company we instantly make tonight, laughing together over our last supper.
"How do you roll up a tortilla?" asks someone.
"Not like that, anyway," chuckles another.
And so our meal goes, in a clamour of clinking cutlery, 'pass this' and 'pass that, please', kitchen clock ticking away above our heads all the while unheard.
We're even louder after the sugar rush of dessert, clearing up to play cards, then poking fun at the worst dealer, worst hand dealt, totting up terrible scores until night turns our eyes to slits and curled hands can no longer hide our yawns.
The two younger siblings say goodbye before bed. They won't be getting up as early as him, not on their first day back to school. 'See ya, sucker," says one. "Wow," says another, "can't believe you're . . . still here."
He smiles quietly. "Whatever," he says.
We hear him shuffling and thumping around, packing last things long after we close our eyes in the dark.
In the dead of night I roll over and punch the alarm clock into silence. There are already lights in the hall. The house still smells, not unpleasantly, of last night's dinner. We pull on random clothes.
"Will you have breakfast?" I ask the eldest.
"No, thanks," he says.
I take a last gulp of coffee and tug his huge haversack outside. It's still so early that the two dogs barely raise heads from paws. "Ready?" I say, but he's already in the car.
The streets are dark and empty the whole way there as his mother and I issue advisories. "Be careful crossing roads there," she tells him. "Remember, they drive on the wrong side."
"In fact, don't cross any roads at all," I say.
"And be careful swimming," she adds quickly.
"There's sharks," I chime in.
"I was going to say currents," says his mother, "but thank you. Sharks as well. Wonderful."
"And earthquakes," I remind her.
"So," smiles the eldest, leaning forward. "Don't cross roads, or go near water. In fact, don't go out at all?"
"Or if you do, beware of falling rocks," I say.
We pull up to Departures in such good time, I instantly regret getting there quite so fast. Traffic lights just ahead blink and I realise with a pang that we'll be passing these in a minute with an empty seat, still warm.
The lights flash amber as we exchange hugs. "Are you sure you don't want me to come in with you?" says his mother. "Your father can drive around for a bit." He realises she's joking, grins and shakes his head.
The lights ahead turn green as I toot the horn one last time and he turns briefly to wave. They stay green as we trundle through them a second later, the smell of our son's hair still fading in our hands.
Back home we take it in turns to absentmindedly wander into his room to sit on the bed, long after the others have gone to school.
When I go in, I notice all the chocolate he got in his stocking is still stacked on his bedside table.
"We should pack it all up and send it to him," sniffs my wife.
"Yes," I say and I shuffle off go to find a box; something shark and earthquake-proof, something suitable for time travel.