The lid was nailed shut. With an old chisel, Smith prised it open and peeled back the yellowish paper which was revealed. Inside the paper, half-filling the box, there was indeed black powder.
Smith smelled it and poked it around. "It's cordite, all right, and in good condition. But as it's here, it obviously hasn't been used. And anyway, there wouldn't have been anything like enough in this box to have caused that much damage to the house."
"Well," I said weakly, "it was only an idea."
"Nothing wrong with the idea," Smith said. He looked around at the growing collection of discards. "Did you find any detonators?"
He had everyone open every single packet and tin: a lot of rusty staples and nails saw daylight, and old padlocks without keys and rotting batteries, but nothing he could identify as a substance likely to set off an explosion.
"Inconclusive," he said, shrugging, and returned to his rubble.
Yale told Arthur to leave the cordite where it was and do what he liked with the rest, and Arthur began throwing the decaying rubbish into the skip.
I tried to apologise for all the waste of time, but the superintendent stopped me.
"When you saw the tree stump blown up, which of your brothers and sisters were there?"
I sighed, but it had to be faced. "Gervase, Ferdinand and I were always together at that time, but some of the older ones were there too. They used to come for weekends still after they were grown up. Vivien used to make them, so that Malcolm wouldn't cut them out. Alicia hated it. Anyway, I know Lucy was there, because she wrote a poem about roots shrieking blindly to the sky."
Yale looked sceptical.
"She's a poet," I said lamely. "Published."
"The roots poem was published?"
"Yes."
"All right, then. She was there. Who else?" "Someone was carrying Serena on his shoulders when we had to leave the field for the explosion. I think it must have been Thomas. He used to make her laugh."
"How old were you all at that time?" Yale asked.
"I don't know exactly." I thought back. Alicia had swept out not very long after. "Perhaps I was thirteen. Gervase is two years older, Ferdinand one year younger. Lucy would have been… urn… twenty-two, about, and Thomas nineteen. Serena must have been six, at that rate, and Donald… I don't know if he was there or not… he would have been twenty-four."
Yale thoughtfully pulled out his notebook and asked me to repeat the ages, starting with Donald.
"Donald twenty-four, Lucy twenty-two, Thomas nineteen, Gervase fifteen, myself thirteen, Ferdinand twelve, Serena six."
"Right," he said, putting a full-stop.
"But what does it matter, if the cordite is still here?" I said.
"They all saw the force of the explosion," he said. "They all saw it knock the gardener over from a hundred feet away, isn't that what you said?"
I looked at the shattered house and said forlornly, "None of them could have done it."
Yale put his notebook away. "You might be right," he said.
Smith again came over to join us. "You've given me an idea," he said to me. "You and your tree roots. Can you draw me a plan of where the rooms were, exactly, especially those upstairs?"
I said I thought so, and the three of us went into the garage out of the wind, where I laid a piece of paper on the bonnet of Moira's car and did my best.
"The sitting-room stretched all the way between the two thick walls, as you know," I said. "About thirty feet Above that…" I sketched, "there was my room, about eight feet wide, twelve deep, with a window on the short side looking out to the garden. Malcolm's bedroom came next, I suppose about fifteen feet wide and much deeper than mine. The passage outside bent round it… and then his bathroom, also looking out to the garden, with a sort of dressing-room at the back of it which also led out of the bedroom…" I drew it. "Malcolm's whole suite would have been about twenty-two feet wide facing the garden, by about seventeen or eighteen feet deep."
Yale studied the drawing. "Your room and the suite together were more or less identical with the sitting-room, then?" "Yes, I should think so."
"A big house," he commented.
"It used to be bigger. The kitchen was once a morning-room, and where the garage is now there were kitchens and servants' halls. And on the other side, where the passage now goes out into the garden, there were gun-rooms and flower-rooms and music-rooms, a bit of a rabbit warren. I never actually saw the wings, only photographs of them. Malcolm had them pulled down when he inherited the house, to make it easier to deal with without the droves of servants his mother had."
"Hm," he said. "That explains why there are no sideways-facing windows on the ground floor."
"Yes," I agreed.
He borrowed my pen and did some calculations and frowned.
"Where exactly was your father's bed?"
I drew it in. "The bed was against the wall between his room and the large landing which was a sort of upstairs place to sit in, over the hall."
"And your bed?"
"Against the wall between my room and Malcolm's."
Smith considered the plan for some time and then said, "I think the charge here was placed centrally. Did your father by any chance have a chest, or anything, at the foot of his bed?"
"Yes, he did," I said, surprised. "A long box with a padded top for a seat. He kept his tennis things in it, when he used to play."
"Then I'd think that would be where the explosion occurred. Or under your father's bed. But if there was a box at the foot, I'd bet on that." Smith borrowed the pen again for some further calculations and looked finally undecided.
"What's the matter?" I asked.
"Mm… well, because of your tree roots, I was thinking of an explosive that farmers and landowners use sometimes which is safer than cordite. They blow up tree trunks, clear blocked ditches, that sort of thing. You can buy the ingredients anywhere without restrictions and mix it yourself."
"That sounds extraordinary," I said.
He smiled slightly. "It's not so easy to get the detonators to set it off." "What is it, then?" I asked.
Yale, too, was listening with great interest.
"Fertiliser and diesel oil," Smith said.
"What?" I sounded disappointed and Smith's smile expanded.
"Ammonium nitrate," he said. "You can buy it in fine granules from seed merchants and garden cent res places like that. Mix it with fuel oil. Dead simple. As far as I remember, but I'd have to look it up to be sure, it would be sixteen parts fertiliser to one part oil. The only problem is," he scratched his nose, "I think you'd need a good deal of it to do the sort of damage we have here. I mean, again I'd have to look it up, but I seem to remember in be volume in cubic metres over three, answer in kilos."
"What volume?" I asked.
"The volume of the space you want cleared by the explosion."
He looked at the mixed emotions I could feel on my face and dealt at least with the ignorance.
"Say you want effective destruction of everything within a space three metres by three metres by three metres. Twenty-seven cubic metres, OK? Volume of your bedroom, near enough. Divide by three, equals nine. Nine kilos of explosive needed."
"is that," I said slowly, "why reports of terrorist attacks are often so definite about the weight of the bomb used?"
"Absolutely. The area cleared directly relates to the size of the… er… bomb. If you can analyse the type of explosive and measure the area affected, you can tell how much explosive was needed."
Superintendent Yale was nodding as if he knew all that.
"But you don't think this bomb went off in my bedroom," I said.
"No, I don't. Nine kilos of ammonium nitrate in your bedroom would have annihilated it and made a nasty hole all round, but I wouldn't have thought it would bring half a house down. So if we locate the device in that foot-of-the-bed box, we are looking at something in the region of…" he did some more calculations "… say at least seventy-five cubic metres for your father's bedroom… that's twenty-five kilos of explosive."