It was a sunny morning, and there wasn't a single cloud in the sky. Only a tiny white butterfly flew by every now and then, as if to say hello. In the garden, Skye, Ziggy, Lily, and Dash were lying on the grass with their hands held up toward the sun.

"Look!" said Ziggy, wiggling his fingers. "My hand looks like a bunny!"

"And mine looks like a puppy!" laughed Dash, making the shadow of his wrist run across the lawn.

Lily crossed her thumb and pointer finger. "I made a heart!" she said, in her usual confident tone.

Skye, calm as always, slowly spread her fingers and made a long, thin shadow appear on the grass. "Mine is a flower," she whispered, and smiled.

The four children were having fun making shadows when, from far away, a well-known sound arrived.

"CHOO CHOOOO! CHOO CHOOOO!"

The children jumped up. "Toby!" they shouted together.

Toby the Magic Train came puffing through the trees, with his colorful little wagons and a big puff of steam above his chimney. He stopped right in front of them, whistling happily.

"Dear friends, climb aboard, we'll be off in a flash,
to a sweet little clearing through the woods we will dash!
We'll search for a spot, and you must look with care,
for a light is hiding beneath a flower somewhere!"

"Under a flower?" said Lily, surprised. "But light doesn't live under flowers!"

"Maybe today it does!" laughed Ziggy, and he hopped onto the first wagon. The others followed.

Toby whistled happily and off he went. CHOO CHOOOO. They crossed meadows, little streams, and a small wooden bridge. Then they stopped in the middle of a thick forest, in front of a clearing as round as a plate.

The children climbed down with their mouths wide open. The clearing was full of golden flowers, as tall as they were, all looking up at the sun. The petals shone like little gold coins.

"How beautiful!" said Skye.

"It's the Silver Petal Clearing," said a little voice behind them.

The children turned around. On a big green water lily — a water lily is a plant with round leaves that floats on pond water — there was a small green frog, with a tiny shell hanging around her neck on a string of grass. Her legs were crossed and her big eyes were sad.

"But during the day they're gold," the frog continued. "Only at night, when they close, do they show the silver. But tonight… no one will see them."

"Why not?" asked Dash, hopping closer.

The frog sighed. "Because tonight was supposed to be my concert. And I can't sing anymore."

"What's your name?" asked Skye, sweetly.

The frog tried a little smile. "I am Gilda. Gilda the Singing Frog." She made a little hop and halfway through she spun around like a tiny ballerina, then landed back on the lily pad. She smelled like fresh mint, because at night she slept among wild mint leaves.

"Nice jump!" said Ziggy, clapping his hands.

But Gilda didn't laugh. She held her shell tight in her paws. "I don't feel like joking today. I did something very silly."

The children sat in a circle around the lily pad.

"Tell us," said Lily, in her usual firm but gentle tone.

Gilda closed her eyes. "Every evening," she began, "the fireflies come here to dance. Fireflies are tiny insects, with little tummies that glow like a little light bulb. They are my choir of lights. When I sing, they switch their lights on and off in time, and the whole forest becomes magical."

"How wonderful!" whispered Skye.

"Yes, it was wonderful," said Gilda. "But last night… I wanted to make everyone laugh. I sang a teasing little song. I made fun of the smallest firefly, the one called Stella, saying her light was as weak as a wet candle. I thought it was a joke. I laughed by myself, before everyone."

"Oh no," said Dash, putting a hand over his mouth.

"Stella was hurt," Gilda continued, and a little tear ran down her face. "All the fireflies turned off their lights. And then… Stella ran away. She went into the forest all alone. And now she's cold, and no one can find her."

The children looked at each other. The sun was still shining bright, but all four of them felt a lump in their throats.

"We have to find her!" said Ziggy, jumping up.

"And we have to help Gilda make peace with the fireflies," added Lily.

Skye, who usually didn't say much, stood up. "We can do two things at once," she said, calmly. "First we'll build a warm shelter, so when we find Stella she'll know where to come. Then we'll think of how to say sorry to the fireflies."

"Shelter!" said Dash. "Yes! Yes!"

They got right to work. Ziggy ran to gather soft moss between the tree roots — moss is that little green carpet that grows on trunks and stones, and it's as soft as a pillow. Lily collected wide leaves and stacked them like roof tiles. Dash found thin twigs and wove them together to make walls. Skye, with gentle hands, picked up some golden petals that had fallen from the tallest flowers.

"Let's put them inside," she said. "When the moon comes up, they'll turn silver and shine. So even if it's nighttime, Stella will see the shelter from far away."

In a little while, under a big bush, a small soft and cozy shelter appeared. It looked like a little fairy house.

But the sun was starting to set. The sky turned pink, then orange. Stella still wasn't there.

Gilda watched everything in silence, sadder and sadder. She held her magic shell close to her chest. That shell was special: when Gilda sang, the shell would tremble and turn her voice into a sweet echo, that rang through the whole forest.

"And now?" asked Lily. "How do we call her?"

Skye walked over to Gilda. She sat next to her, on the edge of the pond.

"Gilda," she said, "you have a magic voice. If you sing, Stella will hear you. But… you have to sing something true. You have to tell her that you're sorry."

Gilda looked up. "But I've never written a sorry song… I only write funny songs!"

"We'll help you," said Ziggy.

The four children began to think. Lily tapped her fingers on her knees to keep the beat. Dash hummed one note, always the same one, until other notes came to him. Ziggy suggested the rhymes. And Skye, who had a quiet heart, suggested the most important words.

"You have to say you were wrong," said Skye. "With no excuses. And that her light isn't weak, it's beautiful."

Gilda wrote and wrote and wrote. Then she lifted her shell.

But just then the sky turned dark. The forest filled with shadows. Night had come, and usually at this hour the fireflies would light up. But tonight, everything was dark. It was a little colder, too.

Dash looked around and moved closer to Skye. Lily and Ziggy stood closer too. The clearing without lights was a strange and quiet place.

"Gilda," whispered Skye, "it's time."

Gilda hopped onto the lily pad. She was trembling. Never had she been so afraid to sing. But she breathed in, lifted her shell, and even before starting she said, in the tiniest voice: "Blep."

It was her habit, every time she opened a concert. But this time she didn't say it loud, and she didn't laugh. She said it just barely, like a promise to come back to being herself.

Then she sang.

She sang that her words had hurt. She sang that Stella's light was like a tiny milky star. She sang that the fireflies were her family, and that without them the forest had no more magic. The shell trembled, and her voice became a sweet echo that crossed the whole forest.

The children listened without breathing.

Then, all of a sudden, behind a bush, a tiny little light appeared. Flickering, weak, but it was there. It was Stella.

"There she is!" whispered Skye, with her heart beating fast.

Stella flew softly toward the shelter the children had built. She went inside. She felt the warmth of the moss and the petals. She glowed even more. And then, as if in answer, another little light came on among the flowers. And another. And another.

One by one, all the fireflies came back. Their golden-yellow lights spread across the clearing like a rain of little stars.

At that very moment, above the clearing, the full moon rose. It was huge, round, and shone with silver light. The golden flowers, which had been closed at sunset, opened the other way: they showed their other side, the silver petals, that reflected the moon like many little mirrors.

The clearing had become a sparkling theater.

"Ooooh," said Ziggy, Lily, Dash, and Skye all together.

Gilda looked at Stella, who was now glowing brightly above the shelter. "Do you forgive me?" she asked, with her voice a little broken.

Stella flew in a circle around Gilda. Her light grew even brighter. "Yes," she shone, as if to say yes.

Then all the fireflies formed a circle. Gilda did a little hop with a half-spin in the middle, landed on the lily pad and said, this time loud and happy: "BLEEEP!"

And the concert began.

Gilda sang, and the fireflies danced, switching their lights on and off in time. The clearing looked like an upside-down sky. The children danced barefoot on the cool grass, laughing. Even Skye, who was usually so quiet, made little spins on her own.

When the song ended, everyone clapped. Gilda made a big bow.

"Thank you, my friends," she said. "Without you, tonight, there would have been no light at all."

Just then, from the path, came the familiar sound. CHOO CHOOOO.

Toby the Magic Train had come back to pick them up. He stopped under the full moon, with his steam turning silver.

"Dear little ones, now it is time to go,
but here in this clearing your hearts can still glow.
When a friend says I'm sorry with all of their heart,
kind, loving words are the sweetest part!"

The children waved goodbye to Gilda and Stella, and to all the fireflies, who shone together like a great farewell. Then they climbed onto the wagons.

As Toby took them home, Skye looked at the moon from the window. She thought that words, when they are right, are like little lights. They can light up again a heart that had gone dark.

And she smiled, while the magic train whistled happily under the full moon.