A man in a dark jacket

By lunchtime the police had a suspect. A young man called Dev had been seen near the school gate on Thursday evening, asking students questions about Silver Blaze. He wrote for a technology blog, and he was friends with several students at Northfield Academy, the school that had come second in the championship last year.

"He came to sabotage our robot so that Northfield could win," said Ryan, the team captain. Nobody had any proof, but Ryan repeated it so often that soon half the school believed it.

Dev was adamant that he was innocent. "I asked a few questions for an article," he told the police. "I went home at eight. I have never been inside your lab." His jacket, however, was dark blue.

Amira went to see Inspector Lim, who was in charge of the case. "To be honest, the evidence against Dev is inconclusive," he admitted. "There was a smudge of oil on the lab door, but anyone could have left it. And Mr Stratton only saw the man from behind."

Amira went to the canteen next. The cook, Puan Siti, was still upset, and Pak Hassan, still a little groggy, was sitting with her.

"People keep trying to insinuate that I put something in his food," Puan Siti said. "Yes, I made the curry. But Mr Stratton asked me himself, on Wednesday, to cook a special curry for Pak Hassan, as a thank-you. He wanted it extra hot."

Amira thought about this. Only a very pungent curry could hide the bitter taste of the medicine. Whoever had planned the crime had known exactly what Pak Hassan would eat that night.

"So it was someone inside the school," said her friend Wei Jie.

"That's only a conjecture," said Amira. "But it is a better one than Ryan's."