It was a summer evening, and the four friends were lying on a soft blanket in the meadow behind the house. They had just finished eating slices of sweet, cool melon, and now they watched the sky turn dark as velvet.

"Look!" said Ziggy, pointing high up. "A running star!"

A golden trail streaked across the sky. Then another. And right after, another one.

"They're shooting stars!" shouted Dash, jumping to his feet. "They run faster than me! And I'm super fast!"

Skye laughed under her breath, her eyes shining like two little lanterns. Lily, instead, had gone quiet. She was staring at one exact spot in the sky, her eyebrows furrowed.

"Something's wrong," said Lily. Her voice was firm, as always. "Look at the rainbow up there."

The other three looked up. In the middle of the stars a rainbow was glowing. But it wasn't a rainbow like the ones you see after the rain: this one was made of moonlight and tiny stars, and it shone in the heart of the night.

"A rainbow at night?" said Ziggy, his mouth wide open.

"It's called the Night Rainbow," whispered Skye, hugging her shoulders in wonder.

But Lily was right. Something really was wrong. In the middle of all those colors there was a dark empty gap, like a missing tooth in a smile. The rainbow was missing a color. It wasn't whole anymore.

"We have to do something," said Lily, and she clenched her fists. "We can't leave it like this."

Right at that moment, from the far end of the meadow, came a sound that all the children knew very well.

"CHOO CHOO! CHOO CHOO!"

It was Toby the Magic Train! He popped up through the grass all sparkly, with smoke that smelled of cotton candy and wheels that threw off golden sparks. Toby stopped in front of them, blew his little whistle, and said:

"Good evening, children, calm and bright,
climb in my wagons for a flight!
Up high a color's gone astray,
a shy little singer will light the way!"

The four friends looked at each other with shining eyes. A shy singer? Who could it be? Without thinking twice they climbed into the soft wagons, and Toby set off upward, higher and higher, past the rooftops, past the clouds, straight into the starry sky.

And up there something incredible happened. The sky was not empty. It was as soft as an enormous cushion of blue velvet. The stars were close, very close, as big as little pebbles of light, and you could jump from one to another. The clouds were soft to step on, and the trails of the shooting stars glowed like golden slides.

"How wonderful!" said Skye, on tiptoe.

Toby let them off onto a big cloud and, with one last puff, waved goodbye. He would wait there for them to come back.

"The rainbow is that way," said Lily, pointing into the distance. "Let's go!"

But the journey wasn't so simple. The four friends were walking on the clouds, when all of a sudden the edge turned slippery and Ziggy lost his balance. "Heeelp!" he cried, and slid down a golden trail as if it were a slide at the park.

"Ziggy!" shouted Lily. Without a moment's hesitation she threw herself after him. Down the golden slide, with the wind in her face and her heart pounding. She grabbed Ziggy's hand just as the trail ended, and together they landed on a cloud as soft as a mattress.

"Phew, what a scare," said Ziggy, laughing. "But it was kind of fun too!"

"I told you to be careful," said Lily, but she was smiling. "Come on, let's all hold hands. That way nobody gets lost."

Skye and Dash reached them, sliding down too, and all four held hands. They walked together, one step at a time, closer and closer to the Night Rainbow.

All at once a cold wind rose up. Whoooosh! The tiny stars around them were like many little lanterns, and the wind made them tremble. One, two, three little lights went out all at once, and a piece of the sky turned dark.

"I'm a little scared," said Dash, and for once he didn't feel like joking.

"Don't give up!" said Lily, loud and clear. "Let's stand in front of the stars to shield them from the wind. All together!"

The four friends lined up, side by side, making a shield with their bodies. The wind blew, but the little stars behind them stayed lit and slowly began to shine brightly again. The wind, tired out, went off to sleep.

"We did it!" cheered Skye.

In front of them now was the last obstacle: a cloud split in two, with a dark, deep chasm in the middle. On the other side, in a nest made of soft feathers, something golden was glowing.

"We have to get across there," said Lily, looking at the chasm. She swallowed. It was wide. But then she saw a thin little bridge of light connecting the two clouds. "One at a time, holding hands. I'll go first."

Lily put one foot on the bridge of light. She trembled a little, but she didn't stop. Step after step she crossed, and on the other side she held out her hand to her friends. One by one, Ziggy, Dash, and Skye reached her. They had made it across. All together.

And at last they saw her.

In the nest of feathers there was a big bird as bright as a sunset, with golden wings folded up. It was the golden Phoenix. But she wasn't proud and majestic at all, the way you might expect. She was trembling. She had curled up in a corner, with her little head hidden under a wing.

"Hello," said Lily softly. "We came for the rainbow. It's missing a color."

The Phoenix peeked out with one shy eye. "I know," she whispered in a thin little voice. "That color lives in my voice. Once I used to sing the colors by opening my wings, and each time a different melody would come out, filling the whole firmament."

"Fir-ma-what?" said Ziggy, scratching his head.

"Firmament," repeated the Phoenix. "You don't know what that means?"

The four children shook their heads, curious.

"The firmament," explained the Phoenix with a shy smile, "is the whole sky full of stars. This huge ceiling of light above you. That's what it's called."

"Firmament," repeated Lily quietly, so she wouldn't forget it. "What a beautiful word." Then she turned serious again. "So you just have to open your wings and sing, and the color will come back!"

But the Phoenix drew back, and her feathers stood up with fear. "I can't," she said, and her eyes grew shiny. "I'm too scared. Opening my wings in front of everyone, singing in front of everyone... and what if I get it wrong? I'd rather stay hidden here."

Dash tried to say something. Ziggy tried to convince her. Skye gave her a gentle stroke on the feathers. But the Phoenix kept her wings tightly closed and shook her head.

So Lily came closer, sat down beside her, and looked her straight in the eyes.

"I'm brave," said Lily. "And you're fearful. We're very different, I know. But I'll make you a promise: I won't leave you alone, not even for a moment. I'll stay right here, beside you, while you open your wings. I promise."

The Phoenix looked at her for a long time. Something, deep inside her, slowly grew warm. "Really... would you stay with me?"

"Really," said Lily. "A promise is a promise."

The Phoenix took a big breath. She rose up on her little legs. And she began to open her golden wings, slowly, like a flower blooming at dawn. A warm light spread all around.

But right at that moment, from below, a gust of wind blew again. Whoooosh! The Phoenix got scared. She snapped her wings shut and jumped backward, ready to run away and hide again in the darkest part of her nest.

"No! Come back!" shouted Ziggy, Dash, and Skye.

Lily's heart was pounding very hard. This was the moment. She could have gotten scared too. But no. She reached out her hand and grabbed the tip of the Phoenix's wing, gentle but firm, and she didn't let go.

"I'm here," said Lily, looking her in the eyes. "I promised you, remember? I won't leave you. Open your wings. I won't move a single step."

The Phoenix felt that warm little hand holding her wing. And she understood that Lily would not go away. That the promise was true.

So she stopped trembling. She spread her wings wide, big and golden, and from her throat came the most beautiful melody the children had ever heard. It was a song made of light, and from that light a new color was born, bright and shining, that flew straight up into the sky and went to fill the dark gap in the Night Rainbow.

The rainbow became whole again. It shone brighter than ever, and every one of its colors danced with joy.

"You did it!" said Lily, her eyes shining. "You were so brave!"

"No," said the Phoenix, and for the first time she truly smiled. "We did it. You kept your promise. And that's how I found my courage."

The four friends and the Phoenix hugged under the firmament, while the shooting stars drew golden trails above their heads.

Then, from the edge of the cloud, came the familiar sound again. "CHOO CHOO! CHOO CHOO!" It was Toby the Magic Train, ready to take them back home. The children waved goodbye to the Phoenix and climbed into the wagons. Toby whistled sweetly and said:

"What a grand adventure in the firmament high,
you gave back a color, oh me, oh my!
Remember, dear children, with hearts brave and true:
a promise once made must be kept right through!"

And as the little train went down through the clouds, toward the meadow and toward home, the four friends fell asleep side by side, with warm hearts and smiles on their lips. They had learned a new word, firmament, and something even more important: that a promise, when you make it with your heart, must be kept all the way through. Always.