"I want you to see the ghost's walk," he wrote. "Come along!"

Pa.s.sing the sick father's door, Calvin led Duff Salter up to the garret floor, where a room with rag carpet, dumb-bells, boxing-gloves, theological books, and some pictures far from modest, disclosed the varied tastes of an entailed pulpit's expectant. Calvin drew down the curtain of the one window and lighted a lamp. There was a table in the middle of the floor, and there the two men conducted a silent conversation on the ivory tablets.

"This is my room," wrote Calvin. "I stay here all day when I study or enjoy myself. The governor doesn't come in here to give me any advice or nose around."

"Is Mrs. Knox Van de Lear serious as to religious matters?"

"Very," wrote Calvin, sententiously, and looked at Duff Salter with the most open countenance he had ever been seen to show. Duff merely asked another question:

"Has she a good handwriting? I want to have a small doc.u.ment very neatly written."

Calvin went over to a trunk, unlocked it, and took out a bundle of what appeared to be lady's letters, and selecting one, folded the address back and showed the chirography.

"Jericho! Jerry-cho! cho! O cho!" sneezed Duff Salter. "The most admirable writing I have ever seen."

Calvin took the tablets.

"I have been in receipt of some sundry sums of money from you, Salter, to follow up this Zane mystery. I hope to be able to show you to-night that it has not been misinvested."

"You have had two hundred dollars," wrote Duff Salter. "What are your conclusions?"

"Andrew Zane is in Kensington."

"Where?"

"In the block opposite are several houses belonging to the Zane estate.

One of them stood empty until within a month, when a tenant unknown to the neighborhood, with small furniture and effects--evidently a mere servant--moved in. My brother's wife has taken a deep interest in the Zane murder, and being at home all day, her resort is this room, where she can see, un.o.bserved, the whole _menage_ and movement in the block opposite."

"Why did she feel so much interested?"

"Honor bright!" Calvin wrote. "Well, Mrs. Knox was a great admirer of the late William Zane. They were very intimate--some thought under engagement to marry. Suddenly she accepted my brother, and old Zane turned out to be infatuated with his ward. We may call it rivalry and reminiscence."

"Jer-i-choo-wo!"

Duff Salter, now full of smiles, proffered a pinch of snuff to his host, who declined it, but set out a bottle of brandy in reciprocal friendship.

"Go on," indicated Salter to the tablets.

"One morning, just before daybreak, my brother's wife, glancing out of this window--"

"In this room, you say, before daybreak?"

Calvin looked viciously at Duff Salter, who merely smiled.

"She saw," said Calvin Van de Lear, "an object come out of the trap-door on Zane's old residence and move under shelter of the ridge of the roof to the newly-tenanted dwelling in the same block, and there disappear down the similar trap."

"Jericho! Jericho!--Proceed."

"It was our inference that probably Andrew Zane was making stealthy visits to Agnes, and we applied a test to her. To our astonishment we found she had only seen him once since the murder, and that was the night the bodies were discovered."

"How could you extract that from a self-contained woman like Agnes Wilt?" asked Duff Salter, deeply interested.

"We got it from Podge Byerly."

"Jerusalem!" exclaimed Duff Salter aloud, knocking over the snuff-box and forgetting to sneeze. "Mr. Calvin Van de Lear, it is a d.a.m.ned lie."

Calvin locked up with some surprise but more conceit.

"I'm a first-cla.s.s eavesdropper," he wrote, and held it up on the tablet to Duff's eyes. "We got the fact from Podge's bed-ridden brother, a scamp who destroyed his health by excesses and came back on Podge for support. Knowing how corruptible he was, I got access to him and paid him out of your funds to wheedle out of Podge all that Lady Agnes told her. She had no idea that her brother communicated with any person, as he was unable to walk, and she told him for his amus.e.m.e.nt secrets she never dreamed could go out of the house. We corresponded with him by mail."

"Calvin," wrote Duff Salter, "you never thought of these things yourself."

"To give the devil his credit, my brother's wife suggested that device."

"Jericho-o-o-oh!"

Duff Salter was himself again.

"Well, Salter," continued the heir-apparent of Kensington, "we laid our heads together, and the mystery continued to deepen why Andrew Zane infested the residence of his murdered father if he never revealed himself to the woman he had loved. Not until the discovery that Agnes Wilt had been ruined could we make that out."

They were both looking at each other intently as Duff Salter read the last sentence.

"It then became plain to us," continued Calvin, "that Andrew Zane wanted to abandon the woman he had seduced, as was perfectly natural. He haunted and alarmed the house and kept informed on all its happenings, but cut poor Agnes dead."

"The infamous scoundrel!" exclaimed Duff Salter, looking very dark and serious.

"Now, Salter," continued Calvin, "we had a watch set on that ridge of roofs every night, and another one at the old Zane house, front and rear, and the apparition on the roof was so irregular that we could not understand what occasions it took to come out until we observed that whenever your servant was out of the neighborhood a whole night, the roof-walker was sure to descend into Zane's trap."

"Jer-i-cho-ho-ho!"

"To-night, as we have made ourselves aware, your servant is not in Kensington. We saw him off to Treaty Island. I am watching at this window for the man on the roof. The moment he leaves the trap-door of the tenant's house, it will be entered by officers at the waving of this lamp at my window. One officer will proceed along the roof and station himself on the Zane trap, closing that outlet. At the same time the Zane house will be entered front and rear and searched. The time is due. It is midnight. Come!"

Calvin pointed to a ladder that led from the corner of his study to the roof, and Duff Salter nodded his head acquiescently.

They went up the ladder and thrust their heads into the soft night of early summer.

There was starlight, but no moon.

The engine bell just ceased to toll as they looked forth on the scattered suburb, and at points beheld the Delaware flowing darkly, indicated by occasional lights of vessels reflected upward, and by the very distant lamps on the Camden sh.o.r.e.

Most of the houses within the range of vision were small, patched, and irregular, except where the black walls of the even blocks on some princ.i.p.al streets strode through.

Scarcely a sound, except the tree frogs droning, disturbed the air, and Kensington basked in the midnight like some sleeping village of the plains, stretching out to the fields of cattle and the savory truck farms.

Duff Salter mentally exclaimed: