And now, driven into the corner which he had hoped to avoid, his retentive memory brought back a circumstance well-nigh forgotten.  He addressed Barker, his voice soft-hopeless.

“You mean that Mrs. Lawrence was the woman in the taxicab?”

“Yes, sir.”  The “sir,” which Barker used for the first time was respectful.

“Where had she been during the evening—­after dark of the night of the—­killing?”

“At home—­I believe.”

“You believe?”

“Yes, sir.”

Carroll’s eyes lighted.  His voice cracked out accusingly:  “Don’t you know that that is incorrect?”

Barker shook his head.  “Why, no, sir.  Of course, I ain’t sayin’ positive that she was at home all evenin’, but—­”

“As I understand it,” said Carroll slowly—­“an accommodation train came in just about that time:  isn’t that a fact?”

“Some train came in then—­I don’t know which one it was.”

“Isn’t it a fact that the woman who got into the taxicab had been a passenger on that train:  that she got off with the other passengers, carrying a suit-case?”

“There ain’t nobody can see the passengers get off the trains at the Union Station, Mr. Carroll.  You go down them steps and approach the waitin’ room underground—­crossin’ under the tracks.”

“But you do know that this woman—­whoever she was—­passed through the waiting room with the passengers who came on that train, don’t you?”

“Yes, sir—­she done that, but it don’t mean nothin’.”

“Why don’t it?”

“Well, sir, for one thing—­ain’t it true that the papers said the suit-case she was carryin’ wasn’t hers at all.  Ain’t it a fact that she had Mr. Warren’s suit-case?”

“Well?” Carroll saw his last hope glimmering.

“You see, sir—­Mr. Warren was meetin’ Mrs. Lawrence at the station.  He got there with his suit-case at about ten minutes to twelve.  She got there about ten or fifteen minutes later—­”

“How did she come?”

“On the street car.  And when she come out—­she was alone and it was his suit-case she was carryin’—­the same suit-case he had taken into the station.  The one you found in the taxicab.”

“I see—­” Carroll did not want to believe Barker’s story, but he knew that the man was telling the truth—­or at least that most of what he was saying was true.  The detective seemed crushed with disappointment.  Leverage, seated in the corner of the room, chewing savagely on a big black cigar—­was sorry for his friend:  sorry—­yet proud of the way he was standing the gaff of his chagrin.  Carroll again spoke to Barker—­manner almost apathetic—­

“You know a good deal more about this thing than you’ve told us, don’t you Barker?”

“Yes, sir.”

“Very well:  let’s have your story from the beginning to the end.  I’ll be honest with you:  I believe a good deal of what you’ve told me.  Some of your story I don’t believe.  Other portions of it need substantiation.  But you are mighty close to being charged with murder—­and now is your chance to clear yourself.  Go to it!”