Ginger noticed the rock because it was in the wrong place. She knew that for certain.

It was a round, gray rock about the size of a cantaloupe, sitting beside the narrow path behind her grandparent's house. Ginger had passed it dozens of times. It always rested beside a clump of tall grass, half buried in the dirt, with one flat side facing the path. But on Tuesday morning, the rock was in the middle of the path.

Ginger stopped. She looked at the rock. Then she looked at the empty place beside the grass.

“That’s strange.”

She pushed the rock back where it belonged and continued on her way.

Wednesday morning, it had moved again. This time it was several feet farther down the path. Ginger put her hands on her hips. Rocks did not have legs. They did not roll uphill. And they certainly did not wander around after everyone went to bed.

Someone—or something—was moving it.

Ginger decided she had a mystery.

She crouched beside the rock and examined the ground. There were scratches in the dirt behind it, but no footprints she could see. She checked underneath the grass. Nothing. She looked up into the branches of a nearby tree. A bird stared back at her.

“You’re too small,” Ginger told it.

The bird flew away.

Her first suspect was the wind. The afternoon winds could be strong enough to send trash cans rolling down the street and tumbleweeds bouncing across the road. But Ginger pushed the rock with both hands. It was heavy.

“Not the wind.”

Her second suspect was a dog. Dogs dug holes, buried things, carried sticks, and did all sorts of things that made no sense to people. But there were no paw prints.

Her third suspect was her brother. That seemed extremely possible.

Ginger waited until he came outside. “Have you been moving my rock?”

He stared at her. “Your rock?”

“The gray one.”

“Why would I move a rock?”

“To bother me.”

He thought about that. “I might do that,” he admitted. “But I didn’t.”

Ginger narrowed her eyes. She wasn't completely convinced.

That afternoon, she prepared a trap—not the kind that caught anything, but the kind that caught clues. She smoothed the dirt in a wide circle around the rock until it was almost perfectly flat. Then she sprinkled a thin layer of flour across part of the path. Anything that came near the rock during the night would have to leave tracks.

Before going inside, Ginger pointed at the rock. “Stay there.”

The rock said nothing.

Thursday morning, Ginger raced outside before breakfast.

The rock was gone. Not moved. Gone.

Ginger stared at the empty patch of dirt. Then she saw the trail.

A crooked line crossed the flour. At first she thought it was a footprint, but it wasn't shaped like any foot she knew. It looked more like something had dragged itself through the powder. Ginger followed it. The trail disappeared into the grass, appeared again near the fence, and ended beside a shallow hole beneath a bush.

And there was the rock. Ginger knelt. Something moved underneath it. She jumped backward. The rock moved again. Just a little.

Ginger's eyes widened. Very slowly, she leaned closer.

A small brown head appeared from underneath the edge of the rock. Then two bright eyes. Then a tiny pointed nose.

“A turtle!” Ginger laughed so loudly that the turtle immediately pulled its head back inside its shell. Except, Ginger stopped laughing.

That wasn't the rock.

The turtle's shell was almost exactly the same gray-brown color, and from a distance it certainly looked like a rock. But Ginger could see the real rock now. It was lying several inches away.

She stared at the turtle. Then at the rock. The turtle could explain some of what she had seen. But it couldn't explain that.

Ginger looked around the quiet yard. “Hmm.”

She carried the real rock back to its old place beside the tall grass. Then she moved the turtle gently away from the path and left it alone beneath the bush.

Mystery solved. Mostly.

Friday morning, Ginger went outside to check. The turtle was nowhere to be seen. The path was empty. And the gray rock was exactly where Ginger had left it.

“Good,” she said. She walked past it. Then stopped. Slowly, Ginger turned around.

The rock was sitting in the middle of the path. Ginger stared at it.

There were no footprints. No scratches. No turtle. Nothing.

From somewhere behind the fence came a soft little sound.

Scrrrape.

Ginger smiled.

Maybe the mystery wasn't over after all.