From dawn, the clatter of hammers and the smell of tar carried across the water. Skjoldvik lay in the embrace of the steep slopes, and the fjord coiled like a dark snake, glinting in the sunlight. A longship, the Silver Fox, stood on wooden trestles by the boat shed. Spots of amber resin solidified on its sides like tiny drops of honey. Eira stood on the roof of the shed, with her hands in the pockets of her woollen hood. She was eleven years old and her eyes as bright as ice when it cracks. She liked to watch the world wake up slowly: first the cries of the seagulls, then the laughter of the fishermen, and finally the first smoke from the hearths that glided across the water in long, grey strands. - 'Get down from there before you end up like a herring in the sun,' Leif called out to her. He was a year older and usually thought first and then did. He was carrying a wooden shield on which the reindeer's hair was constantly arranged in the wrong direction. Eira crouched down, slid down the roof and jumped onto the sand. - I already smell like the whole harbour anyway. - You smell of smoke and tar,' Leif admitted with a smile. - And a bit of the sea. Behind them strolled old Snorri, in a jacket stitched from seal skins and with a knife that never rusted. He remembered things that others had long since stopped repeating, and sometimes spoke as if the words were fruit to be carefully peeled. - 'The tides will be low today,' he muttered, looking at a sign stuck in a post by the shore. - The rocks will reveal what they don't usually show. At this, Eira twitched as if someone had touched a string inside her. The tides were the best. That's when the fjord revealed its secrets: passages under rocky overhangs, hiding places among the seaweed, sometimes even whale bones that sounded when you knocked on them. On this day, the wind was soft, but it carried something else with it. Eira sensed it in the air: as if far, far away someone was playing a thin horn. She stopped, listening, but Leif was already knocking the dial against the slat, checking the grip. - 'Do you hear that? - She asked. - Seagulls. And someone who can't drive a peg straight,' he stated, glancing at the boy on the other side of the marina. Snorri only smiled, so that golden crumbs glinted in his grey beard. - Sometimes the fjord sings when it feels like it. Better to have full ears and light feet then. As the sun rose higher, the tide collected the water like a woman's roll off a stone floor. Beneath the cliff, a granite shelf showed itself, usually hiding beneath the waves. From time to time the children would go there with stick and line, searching for amber and the feathers of geese that nestled among the seaweed. Suddenly something rustled above their heads. A raven was perched on the beam of a shed. It was slightly bald at the beak, as if it had once fought someone tougher than itself, and it had a gleam in its eye that Eira knew well. He dropped something and it clattered at their feet. - A souvenir? - Leif asked. Eira picked up a strip of sealskin. There was a mark carved in the middle: a line with three short arms, like the horns of a crescent moon. The skin smelled of resin and salt. - Runes? - Snorri squinted his eyes. - Not the kind you put on graves. Someone had marked the way. A raven cawed and swooped up, then flew towards the cliff, circling just above the exposed shelf. - 'We'll just have a look,' Eira said before Leif could come up with a reasonable argument. - 'Before the water comes back. - 'Just for a moment,' Leif slung his shield over his thong and motioned for her to follow. - 'And we'll be back before Snorri counts where we're not. They walked along the ledge, careful of the slippery moss. Seaweed peeled off the rocks like the hair of a sea giant. When they reached under the overhangs, a raven was waiting, perched on a stalactite. Eira lifted her gaze: there was something in the rock that she had not seen before. A delicate ornament, a tangle of lines and knots, like those on sailors' belts, but old, chafed by waves. - Here,' she whispered. - See. Leif ran his fingers over the stone. Cold dust was left on his skin. - This is not just an ornament. - He tapped his knuckles. The rock answered him with a hollow, deafening sound. Eira fixed her gaze on the spot where the knots passed one into the other, forming something like an opening. She gently slid her fingers in there. She felt the stone give way like soft wood. - Help me. He wrestled the rock with her and pressed on. Something cracked quietly, like ice in a honey cup. A fragment of stone swung away, revealing a gap the width of a child. The smell of cool, long-unmoved dampness wafted into their faces. It was dark inside, but it only took a few steps for their eyes to begin to distinguish shapes. The shelf transitioned into a flat, narrow corridor. Raven jumped inside like the first guide. - 'You mustn't go into caves that no one has talked about,' whispered Leif, but he didn't step back. - 'Because then everyone talks too much. They walked along the damp wall. Eira could feel the summer chill of algae and old salt deposits under her fingers. At the end of the corridor was a small chamber, so low that Leif had to bow his head. On the ground, wrapped in a horsehair net, lay a horn. It was not huge, but heavy, as if it had grains of metal inside. On its edges were intricately carved wolf heads, and between them ran signs that Eira could not read. A few of them, however, Leif knew. - Play when the north breathes - he pronounced carefully. - And... listen for the answer. Eira felt her heart rumbling in her cage. She picked up the horn. It was cool as morning and smooth, until her hand sought a place of its own to embrace it comfortably. - 'Not now,' Leif placed a hand on her wrist. - 'First we have to... But Eira had already put the horn to her lips, not because she wanted to anger her brother. She just felt that the sound was already circulating in the air anyway, waiting for someone to let it out. The first attempt was just a whisper of air. The second - a short, dry grass blow. The third time, the horn rang out in a full, low tone that went through the body like a wave. The sound rolled down the corridor, licked the walls, leapt outwards and flew over the water. For a moment, nothing happened. Then the fjord murmured ... different. As if somewhere far away, farther than sight could reach, someone played a note, the same but older. The echo didn't sound like a reflection. It sounded like an answer. Eira and Leif ran out of the cave onto a rocky shelf. The sun was already skimming the water, and there was a faint ribbon-like glow in the sky that heralded that the night would bring the aurora. A raven soared high and circled, screeching like a Hawaiian. - Can you feel it? - Leif squeezed the fabric at his neck. The wind had changed direction, carried the jasmine note of pine and something else, something like the breath of an ice cave. The water did not move as usual. Instead of small ripples gently kissing the stones, a wide, even streak came from the middle of the fjord, like a shadow flowing beneath the surface. The answer reached them a second time, slower, heavier. The rock beneath their feet vibrated so subtly that they could only read it with their knees. Leif looked at the horn in Eira's hands. - 'Put it away. Let's go and get Snorri. It could be... - he broke off because he couldn't find the right word. Eira hesitated a fraction of a moment. But the echo, that old note, seemed to move a spring in her. She put the horn to her lips once more. This time the sound was shorter, purer, as if she had learned their way of breathing. A streak of light ran from the cliff, thin and blue, and danced on the stone beside their feet, as if someone was drawing a path under their feet. - This is out of the ordinary - Leif took half a step back, but then came back again, as if a rope had been pulled between fear and curiosity and now someone was stretching it. A streak of light followed the overhangs to where they had discovered the entrance. This time the stone itself began to move. The crack line flared like embers under the ash and spread slowly, revealing a fissure wider than before. A chill and something like the smell of old roots gushed from inside, but also... a faint whiff of warmth that no one had expected here. - Can you hear it? - Eira held her breath. Somewhere from the depths, where the light does not reach, there sounded a rhythmic booty... booty... booty..., like the beats of a huge heart or like oars being struck against the water by someone with great force. A raven perched on their shoulder, entangled its claws in Leif's hood and tugged as if to push them forward. - 'We'll just have a look,' Leif said quietly, repeating his own words from a moment ago, but they sounded different now. Eira pressed the horn to her chest and stepped into the gap. The light of the blue streak danced across the walls like water in the sun. They took three steps. Four. The corridor descended slightly. The sound of peeling became clearer and was accompanied by a low, sliding tone lock, as if someone was pushing back a very heavy bolt. Ahead of them, at the end of the corridor, something flashed. It was not a fire or a torch. This light was the colour of ice and the sound of blackberries. The wall, which had previously been hard and solid, now trembled like the taut skin of a drum. Lines carved into the stone - wolf's heads, knots, marks - began to move, arranging themselves in new patterns. - Eira... - Leif drew in air violently. - It's opening up. Behind the wall something moved. Heavily, slowly, as if it was waking up from a dream that had lasted longer than people's memory. From below, where the corridor must have joined the water of the fjord, there sounded a dragging, low tone that could not have come from any human throat. The stone shook, the fissure widened a finger more, and a shadow slid out of the darkness, the outline of something that might have been the prow of a ship or....