That morning the sky had cried all night long. Not a scary storm, no: just a gentle rain, the kind that goes tap tap tap on the windows, like little fingers knocking softly to say good morning.

When the rain stopped, Lily opened the front door and ran into the garden in her yellow boots. Behind her came Ziggy, jumping in the puddles, Skye, calm in her soft sweater, and Dash, fast as always.

"Look what I found!" said Lily, holding up a bottle of soap with its round wand. "Let's make bubbles!"

Ziggy blew first. A tiny bubble came out of the wand, rose up a little and... pop! It burst right away.

"You try, Skye," said Lily.

Skye blew gently. Her bubble rose just a bit too, trembled in the air and... pop! It was gone.

Dash tried, running to make his fly higher. Lily tried, blowing softly and then hard. But all the bubbles did the same thing: they rose a little and then burst, before they ever really flew.

"How strange," said Lily, hands on her hips. "The bubbles don't fly anymore. But they have to fly!"

Right at that moment, from the far end of the garden, came a familiar sound.

"CHOO CHOO!"

It was Toby the Magic Train, with his shiny wheels and colorful smoke puffing from his chimney. He stopped beside the children, blew his little whistle, and said, as always, in rhyme:

"The bubbles this morning forgot how to fly,
but I know a bridge that will lift you up high.
So climb without hurry and hold my hands tight,
adventure is waiting, just up out of sight!"

"A bridge?" asked Lily, her blue eyes shining. "Let's go!"

The four children climbed onto Toby. The little train whistled, set off, and flew up, up, past the wet clouds, all the way to a wonderful place.

In front of them was a giant rainbow. But not an ordinary rainbow, the kind you watch from far away: this one came all the way down to their feet and was made of seven colored bands, one above the other, like seven big soft slides.

"The Bridge of Seven Slides," whispered Skye, her mouth wide open.

Red, orange, yellow, green, light blue, blue, and at the very top, far far away, purple. Each band was a different floor of the sky. But something was wrong: the colors were weak, faded, like a candle about to go out.

A tiny trembling voice came from behind a little cloud.

"Who... who are you?"

The children turned around. Out peeked a little rainbow, no taller than they were, hiding halfway behind the cloud. It had only three colors on it: red, yellow, and light blue. The other four were missing.

"I'm Lily. These are Ziggy, Skye, and Dash. And who are you?"

"I'm Iris," said the little rainbow, taking a step back. "A baby rainbow. But... but I don't know how to make all the colors yet. I only know these three. The others scare me, I'm afraid I'll get them wrong."

"And why is the bridge so faded?" asked Lily.

Iris hung her head. "Because the stars have fallen. At night the stars hang up there, each in its own place, and their light holds up the bridge and makes the bubbles of the whole world fly. But they've fallen from their places, and now the dark is putting them out one by one. If they all go out, the bridge disappears forever."

Lily clenched her fists. "Then let's put the stars back where they belong! Where do we start?"

"You have to climb all the way to the top," said Iris, trembling. "Hang every star back on its band. But you must hurry: the bridge fades color after color. Once a color disappears, there's no going back."

Ziggy looked up. The top, where the purple was, seemed so far away. "It's so high!"

"We'll make it," said Lily. "Together. Let's go!"

They began to climb the red band. It wasn't easy: the slide was steep, and they had to climb up backward, gripping the light like a soft rope. Along the way they found the first fallen stars, cold and dark, scattered across the band. Every time they hung one back in the right place, it lit up with a tiny ting! and sent out a spark.

But as they hung the last star of the red, something terrible happened.

The red band began to fade beneath their feet. The color grew lighter and lighter, more and more see-through.

"Run!" shouted Lily. "The red is disappearing!"

Everyone ran toward the orange band. Ziggy jumped first, then Dash, fast as the wind. But Skye tripped, and Ziggy waited for her, and at that very instant the red vanished completely beneath their feet. Skye and Ziggy hung by their little hands from the edge of the orange, their little legs swinging over nothing.

"Help!" cried Skye. "I can't climb up!"

Dash froze, frightened. Iris hid behind a cloud. But not Lily. Lily lay down on her tummy, stretched out her arm as far as she could, and found a grip in the light.

"Take my hand! I've got you! I won't let go!"

With all her strength, she pulled up Skye first, then Ziggy. They were safe, on the orange, their hearts beating fast.

"Thank you, Lily," said Ziggy, still trembling.

"We never give up," answered Lily. "Never. Now let's climb!"

On they went like this, from band to band. Orange, yellow, green. On every floor they hung the fallen stars, heard them light up ting! ting! ting!, and ran to the next color before the one below could disappear. Iris followed them, a little braver now, lighting up the bands he knew with his three colors: red, yellow, light blue.

But the higher they climbed, the more the dark came down. They reached the light blue, then the blue, more and more tired, higher and higher. Until they reached the last band: the purple, at the top of the bridge.

And there, in the middle, was the last dark constellation. A big picture of black, dark stars, waiting only to light up. It was the last one. If it lit up, the bridge would shine again and the bubbles would fly once more.

"Iris!" said Lily. "It's your turn! Light up the constellation with your purple!"

But Iris stopped. He took a step back, trembling like a little leaf.

"I... I can't," he whispered. "I don't know how to make purple. I've never done it. And what if I get it wrong? Purple is a strange color, an ugly one, it's no good for anything. Better if I don't even try."

"But it's the only color the sky is missing!" said Lily.

At that moment the dark reached the last star. A cold gust swept across the bridge, and all the colors below them began to tremble, ready to go out forever. It seemed like the end of everything.

Skye stepped up to Iris, softly, and took his little hand.

"Iris," she said in a warm voice, "you think your purple is wrong. But we've never seen it. How do you know it's ugly, if you've never tried it?"

Lily looked Iris in the eyes. "We believe in you. The color you're afraid to make is exactly the one everyone is missing. It's not a flaw, Iris. It's your treasure. Try. We're right here."

Iris breathed. He closed his eyes. And for the first time in his life, he let his color come out.

A ray of purple, soft and bright as no one had ever seen, poured out of him and settled onto the last constellation.

Ting! Ting! Ting! Ting! All the stars lit up together, a warm and shining purple. And from there the light raced down the bridge: the blue turned blue again, the light blue turned light blue again, the green, the yellow, the orange, the red, all of them lit up bright once more. The Bridge of Seven Slides shone brighter than ever, and at the very top glowed the purple, the color Iris had thought was wrong.

"You did it!" everyone shouted. "Your purple saved the sky!"

Iris looked at himself, full of purple light, and for the first time he smiled without fear. "It was... it really was my color that was missing. And I thought it was wrong."

Far away, in the garden of the world, millions of soap bubbles began to fly high into the sky, light and happy.

"CHOO CHOO!"

Toby the Magic Train pulled up onto the bridge, his colorful smoke doing loop-the-loops. The children said goodbye to Iris with a big hug and climbed aboard. Toby whistled and said, in rhyme:

"Who looks a bit different is never all wrong,
the strangest of colors kept the whole sky strong.
Now home we go gliding, to bed and to dream,
so hold on tight, friends, through my soft clouds of steam!"

And as Toby drifted down through the clouds, Lily watched the bubbles fly outside the window and smiled. She had learned something important: you must never judge someone by how they look. Sometimes the very thing that seems like a flaw, a strange color, something to hide, is the most precious treasure of all. You just need the courage to show it, and a friend who believes in you.