Mischief leapt into Tinker’s arms and cuddled there. He didn’t like it when Tinker was upset about anything; he knew by the boy’s voice that he was worried. He made small comforting noises, and rubbed his monkey nose against the boy’s chin.

“You’d better go to your father,” said Jenny. “You might be able to comfort him a little. He’s very upset indeed. He’s up in the tower room, trying to sort out his papers. My word, they were left in a state — scattered all over the room!”

Tinker stood up to go, and was astonished to find that he was shaky at the knees. Would his father ask him if he had been talking about the work he was doing?

Oh dear — he had even boasted about it just the day before, and talked about his father’s sko-wheel, and the wonderful new machine, the electric trosymon! Tinker’s knees became shakier than ever.

But fortunately his father was far too upset about his muddled room and missing papers to worry about anything Tinker had said or done. He was up in the tower room, trying to discover which of his papers were missing.

“Ah, Tinker,” he said, when the boy came into the tower room. “Just give me a hand, will you? The thief who came last night must have knocked the whole bunch of papers off the table, down on the floor — and fortunately he seems not to have seen some that went under the table. So I doubt very much if the papers he did take away with him will be of any use. He’d need to be quite a scientist to understand them, without having the ones he left behind.”

“Will he come back for the others, then?” asked Tinker.

“Probably,” said his father. “But I shall hide them somewhere. Can you think of a good hiding-place, Tinker?”

“Dad — don’t you hide them,” begged Tinker. “Not unless you tell me where they are! You know how you forget things! You might forget where you’d put this bunch of papers, and then you wouldn’t be able to go on with your inventions. Have you copies of the stolen sheets of figures and diagrams?”

“No. But they’re all in my head as well as on paper,” said his father. “It will take me a bit of time to work them all out again, but it can be done. It’s a nuisance-especially as I’m working to a date. Now run along, Tinker, please. I’ve work to do.”

Tinker went down the spiral staircase of the tower. He’d have to make sure that his father did hide away those papers very carefully indeed — in some really good place. “Oh dear — I hope he won’t do what he did with the last lot of papers he wanted to hide,” he thought. “He stuffed them up the chimney — and they nearly went up in flames because Jenny thought she’d light the fire the next night, it was unexpectedly so cold. Good thing they fell down when she laid the fire, and she rescued them before they got burnt! Why are brainy people like Dad so silly about ordinary things? I say he’ll either forget where he puts them — or go and hide them in some easy place where anyone could find them!”