Kennedy smiled, unafraid. But from the expression in his eyes I knew that he took the thought of our possible danger very seriously.
XXIV
THE INVISIBLE MENACE
Mackay and I exchanged glances. Kennedy busied himself putting away some of the more important bits of evidence in the case, placing the tiny tubes of solution, the blood smears, and other items together in a cabinet at the farther corner of the laboratory. The vast bulk of his paraphernalia, the array of glass and chemicals and instruments, he left on the table for the morning. Then he faced us again, with a smile.
"Suppose you start up the percolator once more, Walter!" He took a cigar and lighted it from the match I struck. "I believe I've earned another cup of coffee," he added.
Mackay had been fidgeting considerably since Kennedy's explanation of the possible danger to Shirley, as well as to ourselves or even to others.
"Isn't there something we can do, Kennedy?" he exclaimed, suddenly. "Is it necessary to sit back and wait for this unknown to strike again?"
"Ordinarily," Kennedy replied, "on a case like this it has been my custom to permit the guilty parties to betray themselves, as they will do inevitably—especially when I call to my aid the recent discoveries of science for the detection and measurement of fine and almost imperceptible shades of emotion. But now that I realize the presence of this menace I shall become a detective of action; in fact, I shall not stop at any course to hurry matters. The very first thing in the morning I shall go to the studio and I want you and Jameson along. I"—his eyes twinkled; it was the excitement at the prospect—"I may need considerable help in getting the evidence I wish."
"Which is—?" It was I who interposed the question.
Kennedy blew a cloud of smoke. "There are three ways of tracing down a crime, aside from the police method of stool pigeons to betray the criminals and the detective bureau method of cross-examination under pressure, popularly known as the third degree."