So he gave over running—­running after a taxi-cab was not in his line—­and resumed his walk northward.  At Dupont Circle he found a lone cab with a drowsy negro on the box; who came quickly to life, however, at his approach.

“Cab, seh, cab?” he solicited.

“Which way did the yellow taxi go that just came up Connecticut Avenue?” Harleston asked.

“Out Massachu’ts abenu’, seh, yass seh.—­Cab, seh?”

“Drive out Massachusetts Avenue,” Harleston directed, getting in.  “If you see a taxi, get close to it.”

“I’ll do hit, seh, yass seh!” said the negro, as he climbed on the box and jerked the lines.

But though they went out the avenue to beyond Sheridan Circle, and back again, and along the streets north of P and west of Twentieth, no taxi was seen—­nor any trace of Madeline Spencer.  They drove over the route for more than an hour—­and never raised a yellow taxi nor a skirt.  Finally Harleston abandoned the search and headed the cab for the Collingwood.

Miss Williams was on duty when he entered, and she signalled him to the desk.

“The Chateau has been trying to get you for the last half-hour,” said she.  “Shall I call them?”

“If you please,” he replied, “I’ll wait here.”

Presently she nodded to Harleston; he stepped into the booth and closed the door.

“This is Mr. Harleston,” said he.

“I recognize your voice, Guy, dear,” came Madeline Spencer’s soft tones.  “I’d know it anywhere, indeed.”

“The same to you, my lady,” Harleston returned.  “Was that what you were calling me for?”

“No, no!” she laughed.  “I just wanted to tell you that I’m back at the Chateau.  I thought you might be interested, you know; you sprinted so rapidly up N Street, and spent so much time driving around in a cab searching for me, that I assume it will be a very great relief to you to know that I am returned.  It was such a satisfaction, Guy, to feel that you were so solicitous for my safety, and I appreciate it, my dear, I appreciate it.  Meanwhile, you might wish to get busy as to my alter ego.  I saw her going up Sixteenth Street, as I was returning—­a little after eleven o’clock.  Maybe she needs assistance, Guy; you never can tell.  See you tomorrow, old enemy.  Good-bye for tonight.”

“I say—­are you there, Madeline?” Harleston ejaculated; then asked again.  When no one answered he hung up the receiver and came from the booth.  Spencer, that time, had put one over him; two, maybe, for he was concerned about Mrs. Clephane.  Spencer had gone without her shadow, been free to transact her business, and returned—­and all the time she knew of passing him and his pursuit of her, and was enjoying his discomfiture.  To add a trifle more uneasiness, she had thrown in the matter of Mrs. Clephane.  Probably it was false; yet he could not be sure and it troubled him.  All of which, he was aware, Mrs. Spencer intended—­and took a devilish joy in doing.