Children of the Lens by E.E. Smith

In order to understand these and subsequent events it is necessary to cut back briefly some twenty-odd years, to the momentous interview upon chill, dark Onlo between monstrous Kandron and his superior in affairs Boskonian, the unspeakable Alcon, Tyrant of Thrale. At almost the end of that interview, when Kandron had suggested the possibility that his own base had perhaps been vulnerable to Star A Star's insidious manipulations:

"Do you mean to admit that _you_ may have been invaded and searched -- tracelessly? " Alcon fairly shrieked the thought.