Rain had fallen all morning long. A warm and gentle rain, the kind that makes a soft sound on the leaves and leaves the air smelling of wet earth. Skye, Ziggy, Lily and Dash were in the garden with four glass jars, running to catch the last drops that slid down from the roof of the little house.

"I caught seven!" laughed Dash, jumping into a puddle and splashing everyone.

"I caught so many I can't count them anymore," said Lily, her blue eyes shining like two marbles.

Ziggy held his jar up high and tried to catch the drops with his tongue, then did a somersault on the grass. Skye was quieter. She held her jar in her hands and looked at the sky. The rain was ending, and between one cloud and another the sun had peeked out. And then, little by little, a great rainbow drew itself across the sky. Red, orange, yellow, green, blue, indigo and violet: seven colors that made a huge bridge from one hill to another.

"Look," whispered Skye. "It looks like a staircase of colors climbing all the way up to the sky."

Right at that moment they heard a familiar sound. CHOO CHOO! From behind the bushes came Toby the Magic Train, with shiny wheels and a happy whistle that sounded like a party.

"CHOO CHOO, little children, come climb up with me,
a place full of colors is waiting, come see!
Up there lives someone who trembles with fright,
and tonight the big sky has lost all its light."

The four friends didn't need to be told twice. They set down their jars and climbed onto the soft train cars. Toby whistled, started to move, and instead of running on the tracks he climbed right up the rainbow, as if it were a big colored staircase. The higher they went, the smaller the world became below them.

They reached the top, on the Hill of Seven Colors. It was a wonderful place: the grass was soft and changed color at every step, and far off stood a little round house all made of glass, resting on the last color of the rainbow. But something was wrong. The sky, which should have been full of stars, was covered by lots of gray clouds. They had piled up one on top of another, grumpy, with long faces, hiding everything.

"Ugh," said Dash. "It looks like the sky put on a coat that's way too heavy!"

The children laughed, but it was a little laugh, because it was almost dark. That was when they heard a light sound, like the beat of tiny wings. From behind the glass house came a dragonfly. But not just any dragonfly: her wings changed color with the light, now pink, now gold, now blue. She was beautiful. But she was trembling.

"Hello," said Skye in her calm voice. "I'm Skye. And who are you?"

"My name is Iris," answered the dragonfly, in a thread of a voice. "And tonight was supposed to be the most beautiful night of the year. The night of the shooting stars."

"Shooting stars?" asked Ziggy, his eyes wide open.

"Yes," said Iris. "They are stars that run fast across the sky and leave behind a golden trail, like a tail of light. But tonight they won't be able to come."

"And why not?" asked Lily, who never gave up.

Iris led them inside the glass house. In the middle stood a big telescope. It was a long, magic tube, the kind used to look far, far away, until you touch the stars with your eyes. But now it was off, gray, and sad.

"The telescope calls the shooting stars," explained Iris. "It sends a beam of light up high, and the stars follow it to come and say hello to the Moon. But it went out, because it's missing a color. And I... I had made a promise."

The dragonfly lowered her wings.

"Every night of shooting stars," she said, "I had promised to light up the colors of the sky with my wings. So the old Moon, who is a little lonely up there, would never stay in the dark. But tonight I'm too scared. There are so many clouds, everything is dark, and I am small. Nobody sees me anyway. It's better if I give up."

And a little tear ran down her wing.

Skye said nothing. She sat down next to Iris, very close, and spoke to her gently.

"You know, Iris," she began, "sometimes the dark scares me a little too. But my mom made me a promise. She told me: I'll always leave a little light on for you at night, so if you wake up you won't be in the dark. And she kept it. Every night, since the day I was born, that little light is there. Even when I'm tired and fall asleep in her arms, I know it's there."

"And does that help you?" asked Iris.

"So much," said Skye. "Because a promise you keep is like a hug that reaches you even from far away. It warms your heart even when the person who loves you isn't right there. Tonight, the Moon is waiting for your hug."

Iris looked at her. Her wings, for a moment, glowed with a warm color.

"But I'm scared I can't do it," she whispered.

"You're not alone," said Lily, placing a hand near her. "We're here. And when I'm scared, I do one thing: I take a big breath and then I try anyway."

"And if you fall," added Dash with a smile, "I'll catch you in the air! I'm the fastest of everyone, ask anyone!" And he pretended to trip to make Iris laugh. And Iris, just a little, laughed.

But there was still a problem. The telescope was missing a color, and nobody knew which one. Everyone looked at that dark tube without understanding. That was when Ziggy, who always thought in his own special way, stopped. He looked at the telescope. Then he looked at Iris's wings, which changed color in the little bit of light. And an idea lit up inside him, like a light bulb.

"Wait!" shouted Ziggy. "I've got it! The color the telescope is missing isn't just any color. It's exactly the color of Iris's wings! Nobody else in the world has it! Iris, you are the missing color!"

Everyone stood with their mouths open. It was true. Iris's wings made a special light, a color that couldn't be painted or bought.

"Me?" said Iris, still trembling. "But I would have to fly right inside the lens, in the dark..."

The moment had come. Iris looked at the dark telescope and felt all of her fear. Her wings trembled. She took a step back. Then she looked at Skye, who was smiling at her without saying a word, only with her eyes.

"Nobody sees me anyway," Iris whispered again. But then, softly, she added: "...but the Moon is waiting for me. And a promise is a promise."

And so, with a big breath like Lily had taught her, Iris took flight. She flew straight into the lens of the telescope. And in that darkness she began to beat her wings with all the strength she had. One color after another, the lens filled with light: pink, gold, blue, green, all the colors together.

POP! The telescope lit up. From its tip shot a beam of light so strong it pierced the gray clouds like an arrow of sun.

"Look at the sky!" shouted Lily.

Down along that beam of light came a shooting star. Then another, and another. There were so many, with their golden tails, running across the sky like sparks. And when they touched the grumpy clouds, the clouds stopped being angry. They melted away one after another, slowly, and the sky opened up completely.

Up there, at last, you could see the Moon. She was big, round, and she looked truly happy. The shooting stars danced around her, and the Moon was no longer alone. Iris came out of the lens, tired but happy, and her wings weren't trembling anymore.

"I did it," she said. "I kept my promise."

"And look how the Moon is looking at you," said Skye, her eyes a little teary and a big smile on her face. "She sees you, Iris. She always has."

From the sky something white and soft began to fall. It wasn't rain anymore: it was gentle snow. Light flakes coming down without any hurry, settling on the Hill of Seven Colors like lots of little stars on the ground. The children reached out their hands to catch them, and Iris flew among them, happy.

Then, from far away, that sound came again. CHOO CHOO. It was Toby, back to take them home. Iris waved goodbye to everyone with her wings, and most of all she said goodbye to Skye, with a little hug of light.

The children climbed onto the train, tired and happy. Toby whistled sweetly and said:

"CHOO CHOO, time for home now, hold on nice and tight,
you saw the whole sky open up to the light.
A promise you keep is a gift that will fly,
and warms someone lonely, even a moon in the sky."

As they went down along the rainbow, Skye looked up one more time. The Moon was shining, the stars were running, and the snow was falling softly. She thought about her mom and the little light at night. And she understood that Iris, that night, had learned the same thing she already knew: that a promise is a promise, and it must always be kept, even when you're a little scared. Because that's exactly when it becomes the most beautiful gift of all.

When they got home, in the garden, the four glass jars were still there. But inside, instead of the raindrops, now a little golden light was shining. A tiny piece of a shooting star, to remember that promises, when you keep them, stay lit forever.