The Lone Wolf by Louis Joseph Vance

For all that success had rewarded his effrontery, Lanyard's mind was far from easy during the subsequent hour that he spent before attempting to rejoin Lucy Shannon, dodging, ducking and doubling across Paris and back again, with design to confuse and confound any jackals of the Pack that might have picked up his trail as adventitiously as Ekstrom had.

His delight, indeed, in discomfiting his dupe was chilled by apprehension that it were madness, simply because the spy had proved unexpectedly docile, to consider the affaire Ekstrom closed. In the very fact of that docility inhered something strange and ominous, a premonition of evil which was hardly mitigated by finding the girl safe and sound under the wing of madame la concierge, in the little court of private stables, where he rented space for his car, off the rue des Acacias.