Arnold's. Some repartee, or insolence, when reprimanded for smoking (he was described as a tonguey lout) had provoked his discharge and he had been heard to threaten vengeance behind the professor's back, though at the time his words were muttered they were ignored as a braggart's empty vaporing. Twice he had called to see Ellen at the house, but he had not shown his face since the week before the professor died; and even at his favorite haunt, a certain Charles street stable, all trace of him had been lost. As he was a resident of this country for less than a year he may have crossed the water again to his home, but if this were so Bertha felt sure Ellen would have manifested her lonesomeness. "She had a great heart to the man," said the Swedish housemaid.

"Well, what have you collected against him?" said the district attorney, to whom McCausland had just been exhibiting these results of his investigation. They were alone, save for a bloodhound, in the inspector's office at police headquarters.

"Opportunity, motive and circumstances. I don't rule out the other two as accessories, you understand." The "other two" were Mungovan and Ellen Greeley, who with Robert had been arranged in a triangle by the detective.

"That remains to be fitted into the developments, I presume?"

"First, as to circumstances. The young man turns up about 11 o'clock at a fire which started at 3:30, which destroyed his own home, and which was advertised all over the country within a radius of thirty miles before sunset."

"In itself not a very damaging circumstance. It might be explained. You have questioned him on his movements?"

"In two interviews," replied the inspector, puffing his cigar leisurely and watching the smoke curl as though it were the most fascinating study in the world just then.

"Account not satisfactory?"

"He has none to give." (Puff.)

"What does he mean by that?"

"Memory a blank between 3:30 and 7:30." (Puff.)

"Up to some mischief, then."

"A curiously opportune lapse," said the inspector, his eye twinkling humorously. "So much for circumstances after the fact. And now for opportunity."

"Of course the evidence for opportunity will depend upon the inmates of the house. You are convinced of Bertha's candor?"

"On my reputation as an adept in mendacity. You have not found me overcredulous, as a rule?"

"Quite the contrary."

"Bertha was upstairs, Floyd in the study, Ellen, the cook, had just gone out. After awhile the barking of the St. Bernard in the study aroused the girl. Something was wrong. She ran down, opened the study door and fell back before a live crater of smoke and flame. Accident, we agree, is out of the question. The front door was locked. There was no approach to the study (up one flight, remember) from the street, unless you raised a ladder to the window, and half the neighborhood would have seen this. At least I'm sure the bake-shop girl, Senda Wesner, would have seen it. The previous actions of Floyd were those of a criminal meditating crime; his subsequent course until 7:30 he refuses to explain."

"But the motive, McCausland?" said the district attorney gravely. McCausland contracted his beady eyelets till they shone like two pin punctures in a lighted jack-o'-lantern. But a knock at the door delayed his answer. The bloodhound promptly arose, grasped the knob in his forepaws, and turning it skillfully, admitted a mulatto attendant in fatigue uniform, the bloodhound's master patting him approvingly for the performance.

"Officer Costa to see the inspector," said the attendant.

"Send him in," answered McCausland. "One of my fetch-and-carry dogs—willing enough, but no hawk."

"I've looked the matter up," said Officer Costa, saluting, and glancing from McCausland to the district attorney.

"With what result?"

"Dennis Mungovan and Ellen Greeley were privately married on June 18, before Justice of the Peace Gustavus Schwab, at 126 Harlow street," said Costa, as if proud of his morsel of information and its precision of detail.

"Is this our Mungovan?" asked the district attorney, evincing keen interest.

"What was his description, Costa?" said McCausland.

"Native of Ireland, aged 29; a coachman by occupation. The bride a cook, born in New Brunswick."

"Very well done. Will you look over the steerage list of the European steamers for a fortnight back and ahead? We want that couple, if possible."

"I will," answered Costa, in a manner which showed that the compliment was not wasted. Once more McCausland rose and looked out before shutting the door. Evidently this was another of his mannerisms, and perhaps not the least useful, since one never knows what interlopers may be harking about.

"We have connected numbers two and three of the triangle," he resumed as soon as he was fairly seated, "the interests of Mr. and Mrs. Mungovan being presumably identical."

"I cannot; seriously I cannot credit the charge against Floyd," said the district attorney, "in face of the tender relations known to have subsisted between the young man and his uncle."

"Tender"—McCausland's fat face creased all over into dimples of merriment. "Do young men elope with their grandmothers?"

"Not often," answered the district attorney.

"Neither do they dote madly on their crotchety uncles in the slippers and dressing-gowns of 78."

"Even at 78 I should expect consideration from a nephew whom I had taken in as an orphan and raised to wealth and position."

"Wealth and position! Perhaps that's the rub."

"Just what do you mean?"

"I mean that all was not smooth in the Arnold household; that nephew and uncle were cut too near together from the same block of granite to match; that they wrangled constantly and that one of their wrangles led to this very crisis of the will."

"A will?" echoed the district attorney.

"A will" (puff), smiled McCausland, relapsing into silence.

"Prof. Arnold left a will?" repeated the district attorney, slowly, but McCausland only nodded mysteriously and puffed.

"And—and disinherited the nephew?"

"Exactly—cut him down to $20,000."

"Where is this will?"

"This will was burned. It was the cause of the burning." McCausland had lowered his voice, if anything, but the district attorney stood up in horror.

"More wealth changed hands by the destruction of that document," continued the inspector, "than was converted into smoke and ashes by the fire."

"You mean that young Floyd planned to burn up the will which left him a pauper, so that he might obtain his interest as heir-at-law?"

"That's the motive you were asking for when Costa interrupted us. It was clumsily done, wasn't it? But not so clumsily, when you look at it further. The professor kept his valuables in an iron lock-box which he called a safe. To blow it open was dangerous, unless"—McCausland paused to drive his meaning home—"unless the sound of the explosion could be smothered in the general confusion of a fire."

"You attribute the explosions to——"

"Placed the charge himself in a wooden box under the safe. Told Bertha a plausible story to provide against discovery."

"Six human lives to pay for a few paltry dollars."

"Five million dollars! The professor must have left nearly ten and Floyd would have shared them equally with the other nephew. Hardly a paltry figure, $5,000,000! I've seen murder committed for a 10-cent piece."

"But that was manslaughter in the heat of a quarrel."

"To be sure; and by expert Sicilian carvers, with magnifying-glass eyes and tempers formed between Etna and Vesuvius. But $5,000,000 is a fortune, Bigelow."

The district attorney paced up and down, meditating. At last he turned and brought his fist down on the table so hard that the bloodhound bayed.

"This is murder as well as arson. I want that understood."

"I understood it," smiled the inspector.

"Who saw this will?"

"There's no