The young man was growing more excited.  Carroll put out a restraining hand.

“I quite agree with you, my friend—­it was a pretty rotten impression to create; but I shall see that all doubt is removed from the mind of the public when this afternoon’s papers appear.  I have just learned that your sister has an ironclad alibi.”

“You have already learned that?”

“Yes.”

Gresham leaned forward eagerly.

“What makes you sure—­that she did not—­was not—­”

“Suppose I question you—­if you have no objections.”

“Fire away.”

“Where was your sister at midnight last night?”

“At home.”

“Alone?  I mean was any one besides your family there?”

“Yes,” replied Gresham, showing surprise at Carroll’s evident knowledge of facts.

“Who?”

“Evelyn Rogers spent the night with her.  Evelyn’s a seventeen-year-old kid who has had what I believe you call a crush on my sister.  They were together in that house from ten o’clock last night, or earlier, until this morning.  And if you don’t believe that—­”

“But I do.  I have just had a visit from Miss Rogers, and she told me exactly what you have just repeated; so I’m pretty well satisfied that your sister had nothing whatever to do with the affair.  I will take pains to see that this evening’s papers make that quite clear.”

Gresham rose.  A load seemed to have dropped from his shoulders.

“That’s white of you, Carroll!  I appreciate it.”

“Not at all.  I have no desire to cause annoyance or inconvenience where it is unnecessary.  And Miss Rogers told me, with great attention to detail, just why and how it was impossible for your sister to have been anywhere except at home last night.”

“Evelyn’s considerable of a brick, in spite of the fact that she’s more or less minus in the upper story.  And now, if you’re really satisfied, I’ll be going.”

The two men walked to the door together.  They were about of a height; Carroll slightly the heavier of the two.

“You’ve no idea as to the identity of the woman in the taxicab, have you, Gresham?”

“No.  Have you?”

“None whatever; though I fancy something ought to develop in the near future.  The city is discussing it pretty freely?”

“The town’s wild about it.  They don’t understand anything.  It’s tough on my sister.  Hazel is only a kid, and I think she was in love with Warren.  Well, good day, Carroll.”  He extended a firm hand.  “Any time I can be of any help—­”

“Thanks, Gresham.”

Five minutes after Gresham’s departure, Carroll was in his car, headed for the police-station.  He turned the case over and over in a keen, analytic mind which had been refreshed by a night of untroubled sleep.

There were a good many features about it which puzzled him considerably.  While he had not expected that the trail of the mysterious midnight woman would lead to the fiancee of the dead man, the sudden dissipation of that as a clue rather threw him off his balance.  He had reached the end of a trail almost before setting foot upon it.