"Yes."

"Miss Erith's car."

"Thanks," grunted Vaux, climbing into the pretty coupe and cuddling his shanks under a big mink robe, where, presently, he discovered a foot-warmer, and embraced it vigorously between his patent-leather shoes.

It had now become the coldest night on record in New York City.

Fortunately he didn't know that; he merely sat there and hated Fate.

Up the street and into Fifth Avenue glided the car and sped northward through the cold, silvery l.u.s.tre of the arc-lights hanging like globes of moonlit ice from their frozen stalks of bronze.

The n.o.ble avenue was almost deserted; n.o.body cared to face such terrible cold. Few motors were abroad, few omnibuses, and scarcely a wayfarer. Every sound rang metallic in the black and bitter air; the windows of the coupe clouded from his breath; the panels creaked.

At the Plaza he peered fearfully out upon the deserted Circle, where the bronze lady of the fountain, who is supposed to represent Plenty, loomed high in the electric glow, with her magic basket piled high with icicles.

"Yes, plenty of ice," sneered Vaux. "I wish she'd bring us a hod or two of coal."

The wintry landscape of the Park discouraged him profoundly.

"A man's an a.s.s to linger anywhere north of the equator," he grumbled. "d.i.c.kybirds have more sense." And again he thought of the wood fire in the club and the partly empty but steaming gla.s.s, and the aroma it had wafted toward him; and the temperature it must have imparted to "Bill."

He was immersed in arctic gloom when at length the car stopped. A butler admitted him to a brown-stone house, the steps of which had been thoughtfully strewn with furnace cinders.

"Miss Erith?"

"Yes, sir."

"Announce Mr. Vaux, partly frozen."

"The library, if you please, sir," murmured the butler, taking hat and coat.

So Vaux went up stairs with the liveliness of a crippled spider, and Miss Erith came from a glowing fireside to welcome him, giving him a firm and slender hand.

"You ARE cold," she said. "I'm so sorry to have disturbed you this evening."

He said:

"Hum--hum--very kind--m'sure--hum--hum!"

There were two deep armchairs before the blaze; Miss Erith took one, Vaux collapsed upon the other.

She was disturbingly pretty in her evening gown. There were cigarettes on a little table at his elbow, and he lighted one at her suggestion and puffed feebly.

"Which?" she inquired smilingly.

He understood: "Irish, please."

"Hot?"

"Thank you, yes,"

When the butler had brought it, the young man began to regret the Racquet Club less violently.

"It's horribly cold out," he said. "There's scarcely a soul on the streets."

She nodded brightly:

"It's a wonderful night for what we have to do. And I don't mind the cold very much."

"Are you proposing to go OUT?" he asked, alarmed.

"Why, yes. You don't mind, do you?"

"Am _I_ to go, too?"

"Certainly. You gave me only twenty-four hours, and I can't do it alone in that time."

He said nothing, but his thoughts concentrated upon a single unprintable word.

"What have you done with the original Lauffer letter, Mr. Vaux?" she inquired rather nervously.

"The usual. No invisible ink had been used; nothing microscopic.

There was nothing on the letter or envelope, either, except what we saw."

The girl nodded. On a large table behind her chair lay a portfolio.

She turned, drew it toward her, and lifted it into her lap.

"What have you discovered?" he inquired politely, basking in the grateful warmth of the fire.

"Nothing. The cipher is, as I feared, purely arbitrary. It's exasperating, isn't it?"

He nodded, toasting his shins.

"You see," she continued, opening the portfolio, "here is my copy of this wretched cipher letter. I have transferred it to one sheet.

It's nothing but a string of Arabic numbers interspersed with meaningless words. These numbers most probably represent, in the order in which they are written, first the number of the page of some book, then the line on which the word is to be found--say, the tenth line from the top, or maybe from the bottom--and then the position of the word--second from the left or perhaps from the right."

"It's utterly impossible to solve that unless you have the book," he remarked; "therefore, why speculate, Miss Erith?"

"I'm going to try to find the book."

"How?"

"By breaking into the shop of Herman Lauffer."

"House-breaking? Robbery?"

"Yes."

Vaux smiled incredulously: