Children of the Lens by E.E. Smith

Any human or near-human Lensman would have been appalled by the sheer loneliness of Nadreck's long vigil. Almost any one of them would have cursed, fluently and bitterly, when the time came at which he was forced to concede that the being for whom he lay in wait was not going to visit that particular planet.

But utterly unhuman Nadreck was not lonely. In fact, there was no word in the vocabulary of his race even remotely resembling the term in definition, connotation, or implication. From his Galaxy-wide study he had a dim, imperfect idea of what such an emotion or feeling might be, but he could not begin to understand it. Nor was he in the least disturbed by the fact that Kandron did not appear. Instead, he held his orbit until the minute arrived at which the mathematical probability became point nine nine eight that his proposed quarry was not going to appear. Then, as matter-of-factly as though he had merely taken half an hour out for lunch, he abandoned his position and set out upon the course so carefully planned for exactly this event.