On the farthest edge of the blue-green sea, where the coast curled like the tail of a sleeping fox, stood a village called Brindle Bay.

The houses there were painted in cheerful colors, though the wind had faded them over the years. Some were butter-yellow, some pink like seashells, and some blue as a robin’s egg. Every roof had a chimney, every chimney had a gull perched upon it, and every gull knew exactly when the fishing boats would return.

In Brindle Bay lived a boy named Mateo.

Mateo was small for his age, with sandy hair that never stayed flat and bright brown eyes that noticed nearly everything. He noticed where crabs hid beneath wet rocks. He noticed which clouds meant rain and which only meant a cool afternoon. He noticed that the old clock in the bakery lost three minutes every Tuesday.

But most of all, Mateo noticed the lighthouse.

It was not like other lighthouses.

Other lighthouses stood still on rocky points or tiny islands, brave and tall against the waves. But Brindle Bay’s lighthouse walked.

It had four enormous stone legs, each ending in round, flat feet made from black rock. Its tall white tower was striped with red, and at the top, behind shining glass, turned a warm golden lamp. On calm nights, it walked slowly along the coastline.

Thump.

Thump.

Thump.

Its footsteps were gentle enough not to wake sleeping children, but strong enough that cups in kitchen cupboards gave a tiny rattle.

The walking lighthouse had a name. Everyone called it Old Sula.

Nobody knew who had named it. Old Sula had been walking the coast for as long as anyone could remember. It crossed sandy shores, climbed over mossy cliffs, and carefully stepped around tide pools full of silver fish. Wherever sailors needed warning, Old Sula went.

Yet Old Sula did not only warn sailors about sharp rocks, hidden reefs, or stormy weather.

It warned them about dangers that appeared only in dreams.

This was something grown-ups spoke of very quietly, if they spoke of it at all.

Sometimes a sailor would fall asleep aboard a ship, his cheek against a coiled rope, the sea rocking him softly. In his dream, he might see a glowing harbor and steer toward it. But if he followed that harbor in his dream, his waking hands might turn the ship’s wheel toward a reef.

Or a sailor might dream of hearing bells beneath the waves. The bells would sound sweet and sad. If he listened too closely, he might walk right off the deck, thinking there was a stairway down into the moonlit sea.

These dream dangers were tricky. They could not be seen with ordinary eyes.

But Old Sula’s golden light could find them.

And each night, someone had to care for the lighthouse.

For many years, the caretaker had been an old woman named Auntie Safiya. She wore sea-green boots and carried a brass toolbox with stickers of stars on it. She knew how to polish the great lamp, oil Old Sula’s stone knees, and sing the low, humming song that helped the lighthouse know where to walk.

Mateo loved Auntie Safiya.

He brought her honey cakes from the bakery. He fetched buckets of fresh water. He sat near Old Sula’s giant feet and listened to Auntie Safiya’s stories.

“One day,” Mateo told her, “I want to travel with Old Sula.”

Auntie Safiya smiled behind her round spectacles.

“One day,” she said, “Old Sula may ask you.”

Then, one autumn evening, when the moon was thin as a silver fingernail, Auntie Safiya came to Mateo’s house with her brass toolbox.

Her sea-green boots were muddy. Her face looked tired, but happy.

“Mateo,” she said, “my sister lives over the mountains, and she has had a baby. A very tiny baby with very big sneezes. I must go help for a while.”

Mateo’s eyes grew wide.

“Who will care for Old Sula?”

Auntie Safiya looked toward the shore.

Out beyond the windows, the lighthouse’s golden beam was sweeping the dark water.

“Old Sula has chosen,” she said.

Mateo gulped.

“Me?”

“You,” said Auntie Safiya. “You are brave enough to notice things. And gentle enough to listen.”

She opened the brass toolbox. Inside were little bottles of oil, soft polishing cloths, a map of the coastline, three silver keys, and a small blue whistle.

“This whistle is for emergencies,” she said. “Only use it if Old Sula needs help.”

Mateo held it carefully in both hands.

Then Auntie Safiya bent down and whispered, “Remember, dream dangers are strongest when people feel lonely, worried, or too tired to think clearly. The lighthouse does not fight them by shouting. It guides sailors home.”

That night, Mateo packed a wool blanket, two cheese sandwiches, an apple, and his favorite red scarf. His mother kissed his forehead and tucked the scarf snugly around his neck.

“Listen to the lighthouse,” she told him.

“I will,” Mateo promised.

At the shore, Old Sula was waiting.

Its enormous legs were folded beneath it like a resting heron’s. The lighthouse tower rose into the night sky, its lamp glowing softly. A round little door at the bottom swung open with a creak.

Mateo stepped inside.

There was a spiral staircase, climbing and climbing around the inside of the tower. The walls were warm, though the night outside was chilly. Brass pipes ran along the walls, humming softly. Little shelves held jars of dried lavender, spare lamp wicks, and odd seashells.

At the very top was the lantern room.

The great golden lamp stood in the middle, turning slowly. It was not hot like a fire. It felt warm like sunshine on a window ledge.

Mateo dipped a cloth into polishing oil and rubbed the glass panels until they shone.

Then he checked the compass, just as Auntie Safiya had taught him.

“North is there,” he said. “Brindle Bay is behind us. The Moonless Shoals are ahead.”

Old Sula gave a low, stony rumble.

Thump.

It lifted one giant foot.

Thump.

It took another step.

Mateo gripped the rail as the whole lighthouse began to walk along the moonlit coast.

At first, it was wonderful.

They passed cliffs with waterfalls shining like ribbons. They crossed beaches where tiny ghost crabs waved their claws. They walked past a forest of wind-bent pine trees. Owls turned their heads to watch Old Sula go by.

Then Mateo saw something strange.

Far out at sea floated a small fishing boat named The Merry Mackerel. Its little lanterns were dim. On its deck, three sailors were asleep.

Above the boat, the clouds had gathered into a shape that did not belong.

It looked like a huge gray pillow with a mouth.

The mouth opened wide.

Out drifted hundreds of soft, silvery feathers.

Mateo pressed his face to the glass.

“What is that?”

Old Sula’s lamp flickered once.

Then Mateo understood.

It was a Dream Feather Fog.

The feathers floated down onto the sleeping sailors. As each feather touched them, the sailors smiled and sighed.

Their hands began to move.

One sailor, still asleep, stood up and took hold of the wheel.

In his dream, he must have been steering toward somewhere lovely.

But The Merry Mackerel was turning straight toward the Moonless Shoals, where black rocks hid just beneath the water.

Mateo’s heart bumped hard inside his chest.

He hurried to the lamp controls. There were three brass levers. Auntie Safiya had explained them, but only once.

The left lever brightened the light.

The middle lever changed its color.

The right lever sent the light in a gentle pulse.

Mateo remembered her words: “Feather fogs do not like clear, waking colors.”

He pulled the middle lever.

The lamp changed from gold to bright, clear blue.

The beam swept across the sea.

Once.

Twice.

Three times.

The blue light touched the feather fog. The silver feathers wobbled in the air. They floated upward, twisting like bits of paper in the wind.

The gray pillow-cloud made a sleepy, grumbly sound and melted away.

On The Merry Mackerel, the sailor at the wheel blinked.

“Huh?” he said.

Just then he saw the dark line of rocks ahead.

“Shoals!” he cried.

The sailors woke, pulled the wheel around, and steered safely into open water.

They waved their hats toward Old Sula.

Mateo waved back so hard that his red scarf slipped sideways.

“I did it,” he whispered.

Old Sula’s tower gave a pleased little hum.

But the night was not over.

Near midnight, they reached a place called Whispering Cape. The cliffs there were pale and smooth, and the wind made soft whistling noises through their holes. It was a beautiful place in daylight.

At night, it could be troublesome.

Mateo saw another ship beyond the cape. It was a large cargo ship called The Starling, with a tall black funnel and windows glowing faintly along its side.

Many people were sleeping below deck.

Above the ship floated a dark blue mist, as thin as smoke.

From the mist came music.

It was the sound of tiny bells ringing underwater.

Ting.

Ting-ting.

Ting.

The sound was so lovely that Mateo almost forgot to breathe.

Then he noticed the ship’s passengers beginning to appear on deck. They walked slowly, their eyes closed. One by one, they headed toward the side of the ship.

Mateo grabbed the rail.

“The Bell Mist!”

Old Sula stopped walking.

Thump.

Its stone feet planted firmly on the cliff top.

Mateo knew he needed to use the golden lamp, not the blue one. Bell Mist was drawn to lonely hearts. To guide people away from it, the lamp had to make them remember warm places.

But how?

Mateo looked around the lantern room. On a shelf sat jars of dried lavender. Beside them was a tiny old music box. Auntie Safiya must have left it there.

He wound its little key.

A soft tune began to play.

It sounded like someone humming while they folded blankets. Like a kettle singing in a kitchen. Like rain tapping safely on a roof.

Mateo placed the music box beside the lamp and pulled the right brass lever.

The golden light began to pulse in time with the tune.

Warm.

Warm.

Warm.

It flowed across the water like a path made of honey.

The Bell Mist shivered.

Its underwater music grew quieter.

On The Starling, a little girl in a yellow nightdress stopped at the railing. Her eyes fluttered open.

“Mama?” she said.

Her mother, waking nearby, scooped her up in her arms.

All around them, passengers blinked and looked confused. Then they hurried back inside, wrapped in blankets and coats.

The blue mist curled itself into a tiny knot and drifted away toward the stars.

Mateo let out a breath he had not known he was holding.

“You were right,” he told Old Sula. “We don’t have to scare the dangers away. We just have to show people the way back.”

Old Sula’s lamp glowed brighter for a moment.

The rest of the journey was quiet.

They walked past the Sleeping Whale Cove, where waves rolled in and out with deep, sleepy sighs. They crossed a narrow bridge of rock while the tide sparkled below. At last, the sky began to lighten at the edge of the world.

The stars faded one by one.

A pale pink line appeared above the sea.

Old Sula turned toward Brindle Bay.

Thump.

Thump.

Thump.

When they arrived, Mateo climbed down from the lantern room with tired feet and a proud heart. His mother was waiting on the shore with a warm blanket around her shoulders.

“You’ve been traveling all night,” she said, hugging him close.

Mateo nodded.

“Old Sula walked very far.”

“And were there dream dangers?”

“There were,” Mateo said. “But we helped the sailors find their way home.”

His mother smiled.

Behind them, Old Sula folded its great stone legs beneath itself. Its lamp dimmed from gold to a gentle morning glow.

Mateo leaned against one of its warm, rocky feet.

For just a moment, he thought he felt a great, careful pat from high above, as if the lighthouse were saying, Well done, little caretaker.

Then Mateo went home, ate two bowls of porridge, and climbed into bed.

Outside his window, the sea shone quietly beneath the morning sun.

And far along the coastline, Old Sula rested its stone feet, saving its golden light for the next dark night, when sleepy sailors might need someone to help them wake from dangerous dreams and sail safely home.