The scream is shrill and unexpected.
It echoes across the almost empty restaurant, making the waiter jump. I drop a forkful of Arctic char into my lap.
A young woman rushes to the windows, presses her face against the glass and stares into the darkness beyond.
All aglow: The Northern Lights bring their paintbrush touch to the sky above the Hotel Ion, Iceland
The Icelandic sky is alive.
Ignoring the sub-zero temperatures, we sprint outside and stand in ankle-deep snow watching the emerald bands of the Northern Lights swirl.
A honeymooning couple embrace each other tightly, tears staining their cheeks. ‘This is a dream come true,’ says the new bride.
I know what she means.
The spectacle playing out in the skies over Ion – a remote and luxurious hotel deep in the Icelandic wilderness – is a wonder.
And it isn’t the only reason to visit this enthralling part of the world. I am on a self-drive along Iceland’s Golden Circle trail, which takes in a number of sights just outside Reykjavik.
Most visitors tick off Iceland’s waterfalls, tectonic plates and spouting geysers on an organised tour – but there’s another way.
After two busy days in the capital – feasting on puffin at cosy restaurant Prir Frakkar and sipping brennivín (a local schnapps made from fermented potatoes) at Boston, Bjork’s favourite bar – the open road beckons.
And they don’t get much more open than Iceland’s Highway 35. It’s possible to do the whole 170-mile Golden Circle circuit in four hours, but what’s the rush?
Poring over a map, I plot my route in the reverse order to the one that the coach tours take.
The city fades away, vanishing into the rearview mirror replaced with green valleys and brown mountains.
I pull over beside a farm and the Icelandic horses take a break from grazing to wander over and say hello.
Gullfoss waterfall is quiet.
The daytrippers from Reykjavik are yet to arrive, so we take the trail down to the gentle Hvítá River and watch it pick up ferocity as it plummets over the 70ft drop.
A thrilling afternoon follows: criss-crossing the Langjokull glacier on a snowmobile, at high speed – Beyonce and Jay-Z did the same shortly afterwards – and onwards to another of the Golden Circle’s main spots.
We smell the geyser long before we see it; a stench of sulphur among the steaming geothermal pools.
A crowd gathers for the next performance, which takes place roughly every ten minutes.
Eventually, the earth shakes slightly and the piping-hot puddle bubbles before surging skywards 100ft into the air.
With the late afternoon light beginning to soften, we head for Ion, superbly located near Thingvellir National Park, where the North American and Eurasian tectonic plates meet.
It also stood in for Westeros in scenes from Game Of Thrones.
Aside from a power plant next door (don’t be put off, you barely notice it), the industrial-style 45-room hotel, raised on stilts and decked out with driftwood and exposed concrete, has the surrounding mountains, lakes and meadows to itself.
After our dinner is interrupted by the appearance of the aurora borealis, we get in our bathing suits and out to the plunge pool, where the nocturnal performance shows no sign of a curtain call.
We wallow in the warm waters, sipping cocktails under a night sky heaving with stars and the speckled bands of the aurora.