Tonight I am among vampires, drinking coffee in the dark.

Ireland didn't always have a twenty four hour Starbucks. Once, not very long ago, we didn't have Starbucks at all. But now the future is here–how far we have come!–and I'm sitting in the former headquarters of Anglo Irish Bank at 3am on a Thursday, next to the syrupy dregs of a Pumpkin Spice Latte.

It's surprising that this didn't happen sooner. We have McDonalds, takeaways and kebab shops, places you stumble into looking to eat your way back to sobriety. But what if you had nothing to drink in the first place? What if you have a college essay to write, or an early morning shift to wake up for? What if you're an insomniac, or jet-lagged or just lonely, or some dreadful combination of all three?

Which is where a 24-hour coffee shop starts seem sensible. My night starts at a quarter to one, and Stephen's Green is empty but for a few clusters of people celebrating Halloween early. It's cold, and I envy those in fleece onesie costumes (mummies, monsters, giant cats and dogs) and pity those wearing less (sexy vampires, sexy maids, sexy Ebola…). Starbucks is on the side of the green that's usually lined with taxis, radiating light like an alien spaceship. 

Inside it is glassy and neutral, with the air-conditioned feel of an airport. I start to anticipate a voice over an intercom. It's full of people staring into their phones in pious silence, like some order of futuristic coffee-drinking monks. This is not somewhere you slouch up to half-drunk or with your pajamas on under your coat: this place is clean and mahogany and metallic, like a Sims version of a cafe brought to life. A security guard does the rounds, but it feels safe here: as with Tiffany's nothing bad could happen at 24-hour Starbucks.

I was in school when the first Irish Starbucks opened, in Dundrum in 2005. I was in thrall to anything American–sitcoms, clothing brands, inflected sentences–and for some reason believed that culture could be measured in the number of syrup options on offer (caramel, peppermint, hazelnut, vanilla, vanilla sugar free…). I duly embarked on my very own Orange Mocha-Chip Frappuccino Years.

These days I go to Starbucks once or twice per year at most. I've even managed to bypass their big social media coup, the Pumpkin Spice Latte. But odd things start to seem like good ideas after dark: kebabs, lap dancing clubs, last-minute trips to Coppers… The Pumpkin Spice Latte is the latest on the list.

People like to point out that they don't actually contain any pumpkin, actually, but I shudder to think what gourd-blended coffee would taste like. As it is I'm rather disappointed by the Pumpkin Spice Latte: it tastes basic, just as the internet warned. Nutmeg flavoured coffee with an aftertaste of soap. The sugar goes to your head faster than the caffeine: I feel it almost ringing in my ears.

As I get to the end of my latte it thickens, and begins to smell more like pie. My legs twitch under the table, the caffeine finally kicking in, and I start to notice the background music. They play only love songs in the loneliest coffee shop in Dublin: Norah Jones, John Legend, then of all things 2003's Irish entry to the Eurovision, "We've Got the World" by Mickey Joe Harte. I wonder if this is a ploy to charm tourists. If so it's hardly working: I spot two backpackers dozing in the corner, heads cushioned by their own dreadlocks. One of them has a computer perched on his knee, screen still lit up.

The internet never sleeps: somewhere in the world at this minute, someone is sitting alone in Starbucks and uploading a picture of a pumpkin spice latte.

I check my Facebook and Twitter, and watch those marketing emails that arrive only in the middle of the night appear in my inbox. I'm getting a little glazed: it's pushing 3am now, and Starbucks has stopped feeling like reality. There's a key change and Mickey Joe Harte leads a final chorus, and I begin to think I should go home.

At the door a strange thing happens: I stop to take a picture for this review, and end up talking to a rockabilly-looking guy who is smoking in the doorway. He tells me he comes here every night on breaks from his job in a bar on South William Street, that he fell for Lisa, who works here, and kept coming back, and now the two of them are dating. It turns out that not everyone at Vampire Starbucks is transient. They get regulars: paramedics, nurses, Gardai on the night shift, Muslim teenagers who sit out front and perform night prayers in between coffees. At 4am every night a line of airport workers arrive and knock back espressos.

A nocturnal community has formed, different to any other Starbucks in the city. The pace is slower, calmer and more personal. Sometimes, Lisa tells me, she shows up a few hours early for work just to hang around with the rest of the team. 

There's something unexpectedly comforting about this. I remember when I first moved away from home I had a recurring fear that I would wake up in the middle of the night to an empty kitchen, knowing the city had nowhere open overnight. Though it's sinister and strange that Starbucks has laid claim to Dublin nights, it satisfies that apocalyptic impulse. When the end times come, when zombies overrun the streets, we can camp out in the all-night Starbucks and sustain ourselves on Pumpkin Spice Lattes.

Subject of, there are zombies outside, and pumpkins smashed on the pavement. Real pumpkins, because this is nearly Halloween. The street briefly becomes 28 Days Later: I realise that I am the only person not dressed as a zombie, and not drunk. One particularly lurchy member of the undead tries to follow me up Grafton Street. I fight the urge to remove the head and destroy the brain, and shrug him off. I have grand ambitions to drink more coffee when I get home and carry on with my morning, but when I get there I'm awake just long enough to see the sun rise, and then, as all good vampires should do, I finally fall asleep.