That was not likely to prove an easy matter, and, unless Grantley had lost his cunning, the trail of the machine would probably lead to nothing, even if it could be followed. Nevertheless, there seemed to be nothing else to work on.

The chauffeur of the car might have been an accomplice, but it was not necessary to suppose so. It looked as if the wily Grantley had hunted up a machine of the same make as Doctor Lightfoot’s, and had engaged it for a week or a month, paying for it in advance.

There are many cars to be had in New York on such terms, and they are extensively used by people who wish to give the impression, for a limited time, that they own a fine car.

It is a favorite way of overawing visitors; and chauffeurs in various sorts of livery go with the cars, both being always at the command of the renter.

It would not, therefore, have aroused suspicion if Grantley had furnished a livery of his own choice for his temporary chauffeur.

The first step was to ascertain the make of Doctor Lightfoot’s car. Another make might have been used, of course, but it was not likely, since the easiest way to duplicate the machine would have been to choose another having the same lines and color.

“Mine is a Palgrave,” the physician informed Nick, in response to the latter’s question.

“Humph! That made it easy for Grantley,” remarked the detective; “but it won’t be so easy for us. The Palgrave is the favorite car for renting by the week or month, and there are numerous places where that particular machine might have been obtained. We’ll have to go the rounds.”

Nick and his assistants set to work at once, with the help of the telephone directory, which listed the various agencies for automobiles. There were nearly twenty of them, but that meant comparatively little delay, with several investigators at work.

A little over an hour after the search began, Chick “struck oil.”