Leaving Jones in charge of the house and its gruesome burden, McKelvie, Grenville and I drove to Center Street to secure Ruth's release. On the way Grenville asked McKelvie whether he would mind explaining how he first divined the truth. McKelvie obligingly complied.

"I owe my success to Miss Manning's quick-wittedness in leaving us that clue in the secret room. But for that the case might still be hanging fire. Until we discovered the ring I had no suspicions of the real truth of the matter. I merely mistrusted Cunningham, because he was the only clever unprincipled person connected with the case, but I could conceive of no plausible motive which would cause him to commit the crime.

"I had never swallowed that neat account of how Darwin's finger came to be bruised. The reason was deeper than mere sentiment, I felt. When we stumbled on the ring, the truth flashed across my mind. The ring had to be removed because the dead man was Dick, not Darwin. If that were so, then Dick could not have committed suicide. I determined to test my theory.

"I took with me to Water Street a photograph of Darwin taken when he was Dick's age (I had seen it in an old album in the den upstairs when I first examined the house on Riverside Drive). Both Mrs. Bates and Ben Kite recognized it as the picture of the man who had jumped into the river. So far, so good. Dick had been murdered and Darwin was alive. What was the motive? James Gilmore supplied the answer and the case was simplified. With Darwin as the murderer every fact fell into place with the ease of a carefully pieced puzzle.

"Darwin wanted to rid himself of his wife, Darwin knew she had written a love-letter, Darwin knew that Mr. Davies was in the house and would urge Mrs. Darwin to secure the epistle. Also the quarrel with Lee took on a new phase, a scheme for ridding himself of a pair of keen eyes.

"The only question to be solved was the one, Where was Darwin? Was he still in the city or had he left the country? I could not rid myself of the idea that Cunningham had some share in the affair. He was too keenly interested to be a mere on-looker. Could it be that Cunningham was Darwin, I asked myself. I investigated and discovered that the two men were never in the city at the same time, that they had never been seen together, although they were more than lawyer and client. The finding of the one hundred and fifty thousand dollars in Cunningham's strong box clinched the matter for me. I knew that Darwin was not likely to give another man the money which he would need himself with which to get away."

McKelvie paused and turned to me. "Do you remember the night he told us that pleasant fiction about the one hundred and fifty thousand dollars? I was positive then that he was Darwin, but I had no way of proving it and I had no desire to put him on his guard. That is why I advertised for Lee. I wanted to frighten him into thinking I was on to him and so catch him with the goods, which we were able to do, thanks to his own folly."

"And thanks to you, Mrs. Darwin's life has been saved," I said, as he ceased speaking. "I can never repay you for what you have done," and I held out my hand.

He grasped it with an embarrassed laugh. "Don't thank me. I enjoyed running him to earth. I'm glad he got his deserts."

"Did he really mean to kill himself?" I asked presently.

"No. I examined that closet. It had a double purpose. There was a trapdoor in the ceiling as well, and when you pressed a button in the wall a ladder was let down and you could escape over the roof. That was Darwin's plan, but in his haste he touched the wrong spring, for they were near together and it was dark, and so he fell to his death. Thus is evil punished in the end."

"How did Cunningham happen to have a sachet bag embroidered with his initials when Cora did not know him as Cunningham?" I inquired.

"He had foolishly preserved the one she had given him as Darwin. The initials on it were P. D."

"You told me that when I learned the answers to those questions that I should know who committed the crime. Why was it then that Jones and I did not guess the truth the night we heard Lee's story?"

"Because you had no idea of the motive for the crime. Also you answered some of the questions wrong," he replied with a smile.

"Wasn't it odd that Ruth failed to recognize Cunningham as her husband when he spoke to her at the inquest?" I asked.

"No. He kept his voice disguised. Didn't he say he had a bad cold or something of the sort? When I was positive that Cunningham was Darwin I had a second interview with Mrs. Darwin. She told me then that when Cunningham spoke to her she had an impression that she was hearing the voice of her husband, but as she was persuaded that Darwin was dead she thought it must be her own foolish fancy, and so said nothing about it."

I nodded, recalling the puzzled look on Ruth's face when she glanced at Cunningham at the inquest, for which I had at the time been unable to account, and while I waited McKelvie's return in the reception room of the Tombs, I pondered upon the kindness of Fate in having disposed of the man who had stood so long between me and the one desire of my heart. I wondered how I would tell Ruth the actual facts in the case, and was debating the wisdom of enlightening her when McKelvie returned with a beaming smile.

"She'll be here in just a minute," he said, adding quizzically, "You won't need my help in solving this problem, I'll wager," and he waved his hand toward the door.

The next moment Ruth was in my arms.