Ingraham, we had learned, was a bookmaker and all around crooked gambler. His wife and he had separated, but were on good terms. Some fifteen years before, he had been convicted of “assault with intent to kill” in Newark, NJ , and had served two years in the state prison. But the man he had assaulted—one John Pellow—had died of pneumonia in Omaha in 1914.
Ingraham had come to San Francisco for the purpose of opening a gambling club, and all our investigations had tended to show that his activities while in the city had been toward that end alone.
The fingerprints Phels had secured had all turned out to belong to Stacey, the maid, the police detectives, or myself. In short, we had found nothing!
So much for our attempts to learn the motive behind the three murders.
We now dropped that angle and settled down to the detail-studying, patience-taxing grind of picking up the murderer’s trail. From any crime to its author there is a trail. It may be—as in this case—obscure; but, since matter cannot move without disturbing other matter along its path, there always is—there must be—a trail of some sort. And finding and following such trails is what a detective is paid to do.
In the case of a murder it is possible sometimes to take a shortcut to the end of the trail, by first finding the motive. A knowledge of the motive often reduces the field of possibilities; sometimes points directly to the guilty one. It is on this account that murderers are, as a rule, more easily apprehended than any other class of criminals.
But a knowledge of the motive isn’t indispensable—quite a few murder mysteries are solved without its help. And in a fair proportion—say, ten to twenty percent—of cases where men are convicted justly of murder, the motive isn’t clearly shown even at the last, and sometimes is hardly guessed at.