Except for its characters and plot, this book is not a work of the imagination. The methods which the fictitious Trant — one time assistant in a psychological laboratory, now turned detective — here uses to solve the mysteries which present themselves to him, are real methods; the tests he employs are real tests. Though little known to the general public, they are precisely such as are being used daily in the psychological laboratories of the great universities — both in America and Europe — by means of which modern men of science are at last disclosing and denning the workings of that oldest of world-mysteries — the human mind.
