few people have sleepless nights, and even to those few the experience seldom comes. but if a man wake at intervals to concentrate an alert mind on a problem that has baffled him during the day, and those intervals occupy even a quarter of the night hours, he may scarcely be conscious of having slept. and those sleep-divided oases of thought may often be more fruitful both of decision and design than the most wakeful hours of the day.

henri reynard had been engaged for the past two years in a duel which he had not won - so far was he from his goal that he had only recently been able to make a good guess of whom his principal opponents were. now he had progressed so far that he was assured of several names, of whom professor blinkwell, an englishman of international scientific reputation, was not least. he was so sure of blinkwell that, had it been in his power to sentence him without trial, he would have done it in the certainty of a just deed. but suspicion, however strong, is not proof, of which he owned to himself that he had none. scotland yard which had first suggested blinkwell as the probable head of the english operations of the gang, had to admit the same difficulty. now, the fact that blinkwell had come to paris confirmed these presumptions. but, in itself, it was of no evidential value. to visit paris was not a crime.

yet the hunt was up. a large parcel of illicit drugs, designed to be realized at a huge profit among english addicts, had been nearly seized. the channels used for conveying previous parcels to england had been blocked. beyond that, the places for secure hiding in paris had been exposed. it had become precarious to keep it longer in paris, and perilous to attempt its transit to england. and now the temptation to attempt that transit must be extreme; for the english police admitted frankly that, if it could not be seized en route, they had no clue to the hands into which it would afterwards pass. the closer the paris hunt, the more arrests that were made, the stronger the inducement would be to take the path, however perilous, at the end of which both profit and safety lay. and now blinkwell, departing, it seemed, from his usual aloofness, had come himself to oversee, if not to conduct, the operations which the occasion required.

m. reynard's wakeful hours, it might be thought, would be engaged upon subtle plans for trapping the man of whose guilt he was so confidently assured. but this idea would be wrong. through the night hours he was professor blinkwell, not a chief of paris police. ceaselessly, he contrived plans to baffle the customs officers, casting them aside, one by one, as he saw their flaws. "i must think," he told himself time after time, "of something better than that." it was near the dawn when he passed into peaceful sleep with the thought that he had a solution at last. "it is simple," he told himself. "it is about the simplest plan i have had. but it may be the better for that."