The final

On Saturday morning, Silver Blaze stood in the national championship hall, cleaned and shining silver again. Before the first round, Inspector Lim asked everyone involved to meet in a small room behind the stage.

Amira explained what she had found. "Whoever did this asked for a hot curry to hide the medicine. The dog knew him, so she stayed quiet. And he needed the robot out of the lab on the night before the final."

She turned to Mr Stratton, whose wrist was still in a bandage. "You didn't chase anyone. You carried Silver Blaze to the far end of the field yourself, to damage its motor in the dark, so that it would fail today and nobody would know why."

There was a long silence. Then the coach sat down. He looked tired and remorseful.

"A company that supports Northfield offered me money if our robot lost," he said quietly. "I had debts. I told myself it was a small thing, one loose wire. But when I opened the case, the arm swung round and hit my wrist, and the robot rolled away down the hill towards the road. After that I had no qualms about blaming a stranger. I'm sorry."

The company had been unscrupulous, and Mr Stratton had been duplicitous, smiling at his team every day while he planned to ruin their work. Inspector Lim said the new evidence would exonerate both Dev and Pak Hassan completely.

"It was a devious plan," said Wei Jie. "And the dog ruined it by doing nothing."

At three o'clock, Silver Blaze raced through the final maze and won by four seconds. The team was jubilant, shouting and hugging each other in the middle of the hall. Ryan even went over and shook hands with Dev, who had come to watch.

"How did you know?" Ryan asked Amira.

"I didn't, at first," she said. "It was only a conjecture. Then a dog told me the rest."