From ``The Gods Themselves'', by Isaac Asimov.

Officially, Hallam had come in on that fateful morning, noticed the dusty gray pellets gone -- not even the dust on the inside surface remaining -- and clear iron-gray metal in their place. Naturally, he investigated --

But place the official version to one side. It was Dennison. Had he confined himself to a simple negative, or a shrug, the chances are that Hallam would have asked others, then eventually wearied of the unexplained event, put the bottle to one side, and let subsequent tragedy, whether subtle or drastic (depending on how long the ultimate discovery was delayed), guide the future. In any event, it would not have been Hallam who rode the whirlwind to the heights.

With the ``How would you know?'' cutting him down, however, Hallam could only retort wildly, ``I'll show you that I know.''

And after that, nothing could prevent him from going to extremes. The analysis of the metal in the old container became his number-one priority, and his prime goal was to wipe the haughtiness from Denison's thin-nosed face and the perpetual trace of a sneer from his pale lips.

Denison never forgot that moment for it was his own remark that drove Hallam to the Nobel Prize and himself to oblivion.

He had no way of knowing (or if he knew he would not then have cared) that there was an overwhelming stubbornness in Hallam, the mediocrity's frightened need to safeguard his pride, that would carry the day at that time more than all Denison's native brilliance would have.

Hallam moved at once and directly. He carried his metal to the mass spectrometry department. As a radiation chemist it ws a natural move. He knew the technicians there, he had worked with them, and he was forceful. He was forceful to such an effect, indeed, that the job was placed ahead of projects of much greater pith and moment.

The mass spectrographer said eventually, ``Well, it isn't tungsten.''

Hallam's broad and humorless face wrinkled into a harsh smile. ``All right. We'll tell that to Bright-boy Denison. I want a report and --''

``But wait awhile, Dr. Hallam. I'm telling you it's not tungsten, but that doesn't mean I know what it is.''

``What do you mean you don't know what it is.''

``I mean the results are ridiculous.'' The technician thought a while. ``Impossible, actually. The charge-mass ratio is all wrong.''

``All wrong in what way?''

``Too high. It just can't be.''

``Well, then,'' said Hallam and, regardless of the motive that was driving him, his next remark set him on the road to the Nobel Prize and, it might even be argued, a deserved one, ``get the frequency of its characteristic x-radiation and figure out the charge. Don't just sit around and talk about something being impossible.''

It was a troubled technician who came into Hallam's office a few days later.

Hallam ignored the trouble on the other's face -- he was never sensitive -- and said, ``Did you find--'' He then cast a troubled look of his own at Denison, sitting at the desk in his own lab and shut the door. ``Did you find the nuclear charge?''

``Yes, but it's wrong.''

``All right, Tracy. Do it over.''

``I did it over a dozen times. It's wrong.''

``If you made a measurement, that's it. Don't argue with the facts.''

Tracy rubbed his ear and said, ``I've got to, Doc. If I take the measruements seriously, then what you've given me is plutonium-186.''

``Plutonium-186? Plutonium-186?''

``The charge is +94. The mass is 186.''

``But that's impossible. There's no such isotope. There can't be.''

``That's what I'm saying to you. But those are the measurements.''

``But a situation like that leaves the nucleus over fifty neutrons short. You can't have plutonium-186. You couldn't squeeze ninety-four protons into one nucleus with only ninety-two neutrons and expect it to hang together for even a trillion-trillionth of a second.''

``That's what I'm telling you, Doc,'' said Tracy, patiently.

And then Hallam stopped to think. It was tungsten he was missing and one of its isotopes, tungsten-186, was stable. Tungsten-186 had 74 protons and 112 neutrons in its nucleus. Could something have turned twenty neutrons into twenty protons? Surely that was impossible.

``Are there any signs of radioactivity?'' asked Hallam, groping somehow for a road out of the maze.

``I thought of that,'' said the technician. ``It's stable. Absolutely stable.''

``Then it can't be plutonium-186.''

``I keep telling you, Doc.''

Hallam said, hopelessly, ``Well, give me the stuff.''

Alone once more, he sat and looked at the bottle in stpefaction. The most nearly stable isotope of plutonium was plutonium-240, where 146 neutrons were needed to make the 94 protons stick together with some semblance of partial stability.

What could he do now? It was beyond him and he was sorry he had started. After all, he had real work begging to be done, and this thing -- this mystery -- had nothing to do with him. Tracy had made some stupid mistake or the mass spectrometer was out of whack, or --