Destiny Times Three by Fritz Leiber

If you can look into the seeds of time, And say which grain will grow and which will not -- _Macbeth_

Like a mote in the grip of an intangible whirlwind, Clawly whipped through the gray dawn on a steady surge of subtronic power toward the upper levels of the Blue Lorraine. The brighter stars, and Mars, were winking out. Through the visor of his flying togs the rushing air sent a chill to which his blood could not quite respond. He should be home, recuperating from defeat, planning new lines of attack. He should be letting fatigue poisons drain normally from his plasma, instead of knocking them out with stimulol. He should be giving his thoughts a chance to unwind. Or he should have given way to lurking apprehensions and be making a frantic search for Thorn. But the itch of a larger worry was upon him, and until he had done a certain thing, he could not pursue personal interests, or rest.