The artifact, dropped in a corner, was a little like a flower. Six angular petals, which looked as if they were made of Xeelee sheeting, were fixed to a small cylindrical base; the whole thing was about the size of my open hand. An ornament? The readings from my data desk -- physical dimensions, internal structure -- didn't change as I played with the toy in the light of the flashlight laser. Half the base clicked off in my hand. Nothing exciting happened. Well, whatever it was, maybe it would make the Squeem happy and I could get out.

I took it out into the moonlight. "Squeem, are you copying?" I held it in the laser beam, and twisted the base on or off.

The Squeem jabbered excitedly. "Jones! Please repeat the actions performed by your opposable thumb, and observe the data desk. This may be significant."

"Really." I clicked the base on and off, and inspected the exposed underside in the laser light. No features. But a readout trembled on the data desk; the mass was changing.

I experimented. I took away the torch: the change in mass, a slow rise, stopped. Shine the torch, and the mass crept up. And when I replaced the base, no change with or without the torch. "Hey, Squeem," I said slowly, "are you thinking what I'm thinking?"

"Jones, this may be a major find."

I watched the mass of the little flower creep up in the light of the torch. It wasn't much -- about an ounce per second, to be exact -- but it was there. "Energy to mass, right? Direct conversion of the radiant energy of the beam." And the damn thing wasn't even warm in my hand.

I clicked the base back into place; the flower's growth stopped. Evidently, the base was a key; remove it to make the flower work. The Squeem didn't remark on this; for some reason, I didn't point it out. Well, I wasn't asked.

"Jones, return to the flitter at once. Take no further risks in the return of the artifact."

That was what I wanted to hear. I ran through the skull-like town, clutching the flower. The buttlebot scurried ahead. I gasped out, "Hey, this must be what they use to manufacture their construction material. Just stick it out in the sunlight, and let it grow." Presumably the petals, as well as being the end product, were the main receptors of the radiant energy. In which case, the area growth would be exponential. The more area you grow, the more energy you receive; and the more energy you receive, the more area you grow, and...

I thought of experiments to check this out. Listen, I had in my hand a genuine piece of Xeelee magic; it caught my imagination. Of course, the Squeem would be taking the profits. I considered ways to steal the flower...