There, too, was the matter of Gerald Lawrence to be considered.  Evelyn insisted that Gerald was “an old crab” and also that he was of an exceedingly jealous disposition.  If that were true, then his jealousy, coupled with a possible intimacy between Mrs. Lawrence and Warren might have been ample motive for the taxicab tragedy.

It was all rather puzzling.  Carroll’s mind leaped nimbly from one mental trail to another.  He held himself in check, afraid that his deductions were proceeding too swiftly.  He was acutely conscious of the danger of jumping too avidly on this single tangible clue which had come to him after four days of fruitless search.  There was danger, and he knew it, of attaching untoward importance to a combination of circumstances which under other conditions might not have excited him in the slightest degree.

It was there that the case bewildered him—­and he was not slow in confessing his bewilderment.  Up to this moment there had been an appalling dearth of physical clues—­of things upon which a line of investigation could be intelligently based.  And he knew that now something had turned up, he must watch himself lest the circumstance assume unreasonable and unwarranted proportions.

The somber outline of police headquarters bulked in the night.  Carroll swung down the alley, shut off his motor and entered.  He found Leverage in his office and settled at once to a discussion of developments.  But when he would have spoken Leverage cut him off.  Leverage had news—­and Leverage was frankly proud of the fact that he had news.

“Just got an interesting report from Cartwright,” he announced.

“Regarding Barker?” Carroll hitched his chair forward eagerly.

“Yes.”

“What is it?”

“Yesterday afternoon at five o’clock William Barker went to the residence of Mr. and Mrs. Gerald Lawrence.  He was in the house eighteen minutes.”

“Why wasn’t this told me last night?”

“Cartwright didn’t think anything of it.  He included it in his report which was turned in to me this morning.”

“Why did he think it was unimportant?”

“Said he thought Barker was probably looking for a job.”

“And he doesn’t think so now?”

“No-o.  That is:  he thinks circumstances make an investigation worth while.  You see, just a few minutes ago Barker went to the Lawrence home again.  This time he was there four minutes.”

“Does Cartwright know who was at home at that time?”

“He thinks so.  He says a maid let Barker in and that apparently Mrs. Lawrence let him out.  A young girl—­whom Cartwright believes to be Mrs. Lawrence’s sister—­drove up just as Barker was leaving.  She was in the car with some man—­but he didn’t get out.  Then, just a minute ago, Gerald Lawrence reached home.  So the idea is that Mrs. Lawrence was alone with the servants when Barker called.”

“And yet he only remained four minutes?”