“Why, it just occurred to me lately to go scouting around the city, looking at the Warrington holdings, making some personal inquiries as to the conditions of the leases, the character of the tenants, and the uses to which they put the properties.  The police have compiled a list of all the questionable places in the city and I have compared it with the list of our properties.  I hadn’t come to this one yet.  But I shall call up our agent, make him admit it, and cancel that lease.  I’ll close ’em up.  I’ll fight until every—–­”

“No,” interrupted Garrick, quickly, “no—­not yet.  Don’t make any move yet.  I want to find out what the game is.  It may be that it is someone who has tried and failed to get your tenant to come across with graft money.  If we act without finding out first, we might be playing into the hands of this blackmailer.”

Garrick had been holding the letter in his hand, examining it critically.  While he was speaking, he had taken a toothpick and was running it hastily over the words, carefully studying them.  His face was wrinkled, as if he were in deep thought.

Without saying anything more, Garrick walked over to the windows and pulled down the dark shades.  Then he unrolled a huge white sheet at one end of the office.

From a corner he drew out what looked like a flat-topped stand, about the height of his waist, with a curious box-like arrangement on it, in which was a powerful light.  For several minutes, he occupied himself with the adjustment of this machine, switching the light off and on and focussing the lenses.

Then he took the letter to Miss Winslow, laid it flat on the machine, switched on the light and immediately on the sheet appeared a very enlarged copy of the writing.

“This is what has been called a rayograph by a detective of my acquaintance,” explained Garrick.  “In some ways it is much superior to using a microscope.”

He was tracing over the words with a pointer, much as he had already done with the toothpick.

“Now, you must know,” he continued, “or you may not know, but it is a well-proved fact, that those who suffer from various affections of the nerves or heart often betray the fact in their handwriting.  Of course, in cases where the disease has progressed very far it may be evident to the naked eye even in the ordinary handwriting.  But, it is there, to the eye of the expert, even in incipient cases.

“In short,” he continued, engrossed in his subject, “what really happens is that the pen acts as a sort of sphygmograph, registering the pulsations.  I think you can readily see that when the writing is thrown on a screen, enlarged by the rayograph, the tremors of the pen are quite apparent.”

I studied the writing, following his pointer as it went over the lines and I began to understand vaguely what he was driving at.

“The writer of that blackmailing letter,” continued Garrick, “as I have discovered both by hastily running over it with a tooth-pick and, more accurately, by enlarging and studying it with the rayograph, is suffering from a peculiar conjunction of nervous trouble and disease of the heart which is latent and has not yet manifested itself, even to him.”