The Professor’s smile was illuminating, his manner simple but convincing.

“Craig,” he asserted, “is the best servant, the most honest mortal who ever breathed.  He would go any distance out of his way to avoid harming a fly.  I cannot even trust him to procure for me the simplest specimens of insect or animal life.  Apart from this, he is a man of some property which he has no idea what to do with.  He is, I think I may say, too devoted to me to dream of ever leaving my service.”

“You think it would be out of the question, then,” Quest asked, “to associate him with the crime?”

The Professor’s confidence was sublime.

“I could more readily associate you, myself, or young Mr. Rheinholdt here with the affair,” he declared.

His words carried weight.  The little breath of suspicion against the Professor’s servant faded away.  In a moment or two the butler returned.

“It appears, madam,” he announced, “that Mr. Craig left when there was only one person in the kitchen.  He said good-night and closed the door behind him.  It is impossible to say, therefore, by which exit he left the house, but personally I am convinced that, knowing of the reception here to-night, he would not think of using the conservatory.”

“Most unlikely, I should say,” the Professor murmured.  “Craig is a very shy man.  He is at all times at your disposal, Mr. Quest, if you should desire to question him.”

Quest nodded absently.

“My assistant and I,” he announced, “would be glad to make a further examination of the conservatory, if you will kindly leave us alone.”

They obeyed without demur.  Quest took a seat and smoked calmly, with his eyes fixed upon the roof.  Lenora went back to her examination of the overturned plants, the mould, and the whole ground within the immediate environs of the assault.  She abandoned the search at last, however, and came back to Quest’s side.  He threw away his cigar and rose.

“Nothing there?” he asked laconically.

“Not a thing,” Lenora admitted.

Quest led the way towards the door.

“Lenora,” he decided, “we are up against something big.  There’s a new hand at work somewhere.”

“No theories yet, Mr. Quest?” she asked, smiling.

“Not the ghost of one,” he admitted gloomily.

* * * * *

Along the rain-swept causeway of Mayton Avenue, keeping close to the shelter of the houses, his mackintosh turned up to his ears, his hands buried in his pockets, a man walked swiftly along.  At every block he hesitated and looked around him.  His manner was cautious, almost furtive.  Once the glare of an electric light fell upon his face, a face pallid with fear, almost hopeless with despair.  He walked quickly, yet he seemed to have little idea as to his direction.  Suddenly he paused.  He was passing a great building, brilliantly lit.  For a moment he thought that it was some place of entertainment.  The thought of entering seemed to occur to him.  Then he felt a firm touch upon his arm, a man in uniform spoke to him.