It was a sweet spring evening, and Ziggy was playing in the garden with Lily, Skye and Dash. They each held a little wand for soap bubbles, and every time they blew, out came a big round bubble that floated in the air like a tiny see-through moon.

"Look at mine!" said Ziggy, laughing, as a huge bubble rose above the head of Sofia, his little black cat. Sofia watched it with round eyes, and next to her Dora, the tabby cat, made a curious little hop. Poldo, fat and calm, was sitting on the grass watching. Milo, his brother, was making big leaps in the air to try to catch the bubbles.

"Mine is bigger!" said Lily, proudly, with her blue eyes shining.

"Mine are like little moon balloons," whispered Skye, who was the quietest of the group.

Dash meanwhile was running back and forth, blowing and laughing, because he couldn't stay still.

While they were playing, something began to change. A light mist slipped between the bushes, soft as a cotton blanket. It wasn't a cold mist, it wasn't a scary mist. It was a mist that smelled like grass and evening.

"Oooh," said Dash, "it's like the garden has turned into a dream."

The cats pricked up their ears. Sofia purred, and Milo came close to Ziggy, as if to say: "Something wonderful is happening."

And then, from inside the mist, came a sound the children knew very well.

"CHOO CHOO CHOO!"

It was Toby, the Magic Train! He popped out of the mist with his colorful lights, and stopped right at the end of the garden. He had a big smile painted on the front, and from his chimney came smoke that looked like cotton candy.

Toby the Magic Train gave a gentle whistle and said:

"Good evening, dear children, come climb right up here,
the mist is a doorway, with magic so near!
There's no moon in the sky, but a soft little light
shines under a tent that is gentle tonight."

The children looked at each other and burst out laughing with joy. They climbed onto the little carriage, and the cats stayed in the garden waving with their tails. Toby moved slowly, into the mist that was getting softer and softer.

When the mist opened a little, before the children's eyes appeared something wonderful: a big circus tent. It was huge, with peaks, with colorful stripes. But... the stripes were faded. It looked like a drawing made with almost-finished crayons.

"We're at the circus!" said Ziggy, jumping down from the train.

There was a sign above the tent: "New Moon Circus."

"What does New Moon mean?" asked Skye.

"It's when you can't see the moon in the sky," answered Lily. "My daddy told me."

They went inside the tent. Inside there were acrobats, but they were pale, like tired little ghosts. The clowns had red noses, but they weren't laughing. Even the light animals, which usually sparkled, looked like almost-empty little bulbs.

"What's happening here?" whispered Dash.

A kind clown, with a floppy hat, pointed to a little door behind the ring. It was a small opening in the floor, with stone steps going down under the circus.

"It's a secret cave," said Lily, who was the bravest.

They went down slowly, holding hands. The cave was like a big stone egg, and in the middle there were seven crystals as big as pumpkins. They sparkled, but not all of them. Three were already out, black as coal. The other four shone, but one flickered like a candle near the wind.

And then something magical happened. From behind a crystal, a little creature appeared. He was a baby rainbow, small as a pillow, made of soft colors. He had a glass shell around his neck, and he smelled like fresh rain and wet petals.

He moved in little hops, like a drop that bounces.

"Um... hi," he said, with a sweet little voice. "My name is Iri."

"You're a rainbow!" shouted Dash, happily.

Iri blushed, and from his arc one color slipped away, sliding into the mist that was still at the back of the cave.

"Oh no, my yellow ran away," whispered Iri. "It happens to me when I get excited. I've already lost three, you know? They're in the mist, somewhere."

Ziggy came up to him slowly. "It doesn't matter, Iri. You're beautiful anyway."

Iri smiled a little.

"But the crystals are going out," he said sadly. "And if they all go out, the New Moon Circus won't be able to come back on moonless nights anymore. And without the circus, even the children who come to dream here won't be able to come anymore."

"Can we help you?" asked Lily, firmly.

Iri nodded. "There would be a potion. A potion that brings light back to the crystals. But it's not made with ingredients you gather while walking."

"Then how is it made?" asked Skye, with wide eyes.

Iri picked up a tiny glass bowl that was resting on a rock. It was empty, light, see-through.

"The drops of the potion only appear when someone says a thank-you. A real thank-you, though. A thank-you from the heart."

The children looked at each other. It seemed like an easy thing, but also a new thing.

"I'll try," said Ziggy. He cleared his throat, looked at Skye and said: "Thank you, Skye, because when you smile you look like a little star."

And in that moment, Iri's glass shell went "tin," like a tiny little bell. Inside the bowl a glowing drop appeared, yellow as honey. And one of the dim crystals, the first in the row, lit up again with a sweet song, like a little voice saying "light."

"It's working!" said Dash, jumping on the spot.

Lily came up to Dash. "Thank you, Dash, because when you run, everyone laughs and we feel cheerful."

"Tin." Another drop. Another crystal that lit up.

Skye looked at Lily and said, with her calm voice: "Thank you, Lily, because when you're scared you don't show it, and that's real courage."

"Tin." The third drop fell into the bowl, round as a pearl. The third crystal lit up.

Now four crystals were lit, and in the cave light was beginning to return.

Iri was clapping his hands, and as he was happy, one color came back from the mist and put itself back in its place on the arc. The blue! Iri laughed in surprise.

"They're coming back," he whispered, with shining eyes.

But suddenly, one of the still-dim crystals made a strange noise. It didn't light up. In fact: even one of the lit crystals went out. The whole cave shook for a moment.

"Ah!" said Dash, scared. "Something bad is happening."

"It means the thank-yous have to always be real," said Iri, with a trembling little voice. "If one doesn't really come from the heart, the magic gets confused."

They tried again. Ziggy thanked Dash for the way he played the clown when he wanted to make them laugh. "Tin." A drop. A crystal lit up.

Lily thanked Skye for when she lent her her crayons. "Tin." Another drop. Another crystal.

Only one crystal was left. The last one. The biggest one, at the back of the cave. It was black as night, and seemed the hardest.

The children stopped. They had said so many thank-yous. Had they run out?

And now the worst moment came: the crystal that was still flickering went out completely. In the cave an almost-full darkness fell. Only the last lit crystals made a small light, like a little candle at the back of a room.

Iri was shaking. Even the red color slipped away from him, and hid in the mist.

"Oh no," whispered Skye. "Iri is disappearing."

Ziggy felt his heart beating fast. He was scared, but he really wanted to help. He thought about what had happened that evening. He thought about his friends, he thought about the cats, he thought about himself, who had been brave.

And then he came up to Iri, took his soft little hand, and said in a low voice:

"Thank you, Iri. Thank you because you showed us the cave, even though you were scared. Thank you because you came out of hiding to talk to us. And... thank you also to me, because I didn't run away when the darkness came."

The glass shell made the sweetest "tin" of the whole evening. A huge drop fell into the bowl, and inside the bowl there was now a potion that glowed like liquid gold.

Iri took the bowl with two little hands, and poured it over the last crystal. The crystal lit up all at once, like a small, silent firework. And then all the other crystals answered, singing together a sweet sound, that seemed like the lullaby of the stars.

Iri's red and yellow came back, sliding out from the mist. Iri's rainbow was whole again, all seven colors in their place.

The children ran out of the cave. Above the tent, the mist had opened. And there was a wonderful starry sky, full of shining dots that looked like so many crystals hanging in the sky.

The acrobats had their color back, the clowns were laughing loudly, and the light animals shone like new bulbs.

Iri waved goodbye to the children with a little hop, and his glass shell made the last "tin" of the evening.

"Thank you," said Iri. "Now I'll go back to the bottom of the cave, but I won't hide anymore."

It was time to go home. Toby the Magic Train was waiting for them at the entrance of the tent, steaming and kind. The children climbed slowly onto the little carriage, and Toby gave a small whistle.

Then he said, in rhyme:

"Under the stars, deep inside of your heart,
a thank-you is shining — the loveliest part.
Let's go back home now, my dear little friends,
with a thank-you that shines as our journey now ends."

The little train moved, gently, into the mist that was now light as powdered sugar. And when the children got off in the garden, the four cats ran to greet them, and from the sky a tiny star fell, which looked like a smile.