"Quick," she said, "look for page 17!"

"Yes, I have it!"

"First column!"

"Yes."

"Now try the twentieth word from the top!"

He counted downward very carefully.

"It is the word 'anagraph,'" he said; and she wrote it down.

"Also, we had better try the twentieth word counting from the bottom of the page up," she said. "It might possibly be that."

"The twentieth word, counting from the bottom of the column upward, is the word 'an,'" he said. She wrote it.

"Now," she continued, "try page 15, second column, third word from TOP!"

"'Ambrosia' is the word."

"Try the third word from the BOTTOM."

"'American.'"

She pointed to the four words which she had written. Counting from the TOP of the page downward the first two words were "Anagraph ambrosia." But counting from the BOTTOM upward the two words formed the phrase: "AN AMERICAN."

"Try page 730, first column, seventh word from the bottom," she said, controlling her excitement with an effort.

"The word is 'who.'"

"Page 212, second column, first word!"

"'For.'"

"Page 507, first column, seventh word!"

"'Reasons.'"

"We have the key!" she exclaimed. "Look at what I've written!--'An American who for reasons!' And here, in the cipher letter, it goes on--'of the most'--Do you see?"

"It certainly looks like the key," he said. "But we'd better try another word or two."

"Try page 717, first column, ninth word."

"The word is 'vital.'"

"Page 274, second column, second word."

"'Importance!'"

"It is the key! Here is what I have written: 'An American who for reasons, of the most vital importance!' Quick. We don't want a Secret Service man to find us here, Mr. Vaux! He'd object to our removing this book from Lauffer's apartment. Put it into your pocket and run!" And the pretty Miss Erith turned and took to her heels with Vaux after her.

Through the disordered apartment and down the stairs they sped, out into the icy darkness and around the corner, where her car stood, engine running, and a blanket over the hood.

As soon as the chauffeur espied them he whisked off the blanket; Miss Erith said: "Home!" and jumped in, and Vaux followed.

Deep under the fur robe they burrowed, shivering more from sheer excitement than from cold, and the car flew across to Fifth Avenue and then northward along deserted sidewalks and a wintry park, where naked trees and shrubs stood stark as iron in the l.u.s.tre of the white electric lamps.

"That time the Secret Service made a mess of it," he said with a nervous laugh. "Did you notice Ca.s.sidy's grin of triumph?"

"Poor Ca.s.sidy," she said.

"I don't know. He b.u.t.ted in."

"All the services are working at cross-purposes. It's a pity."

"Well, Ca.s.sidy got his man. That's practically all he came for.

Evidently he never heard of a code-book in connection with Lauffer's activities. That diagonal cipher caught him."

"What luck," she murmured, "that you noticed that cook-book in the pantry! And what common sense you displayed in smuggling it!"

"I didn't suppose it was THE book; I just took a chance."

"To take a chance is the best way to make good, isn't it?" she said, laughing. "Oh, I am so thrilled, Mr. Vaux! I shall sit up all night over my darling cipher and my fascinating code-book-dictionary."

"Will you be down in the morning?" he inquired.

"Of course. Then to-morrow evening, if you will come to my house, I shall expect to show you the entire letter neatly deciphered."

"Fine!" he exclaimed as the car stopped before her door.

She insisted on sending him home in her car, and he was very grateful; so when he had seen her safely inside her house with the cook-book-dictionary clasped in her arms and a most enchanting smile on her pretty face, he made his adieux, descended the steps, and her car whirled him swiftly homeward through the arctic night.

CHAPTER II

THE SLIP

When Clifford Vaux arrived at a certain huge building now mostly devoted to Government work connected with the war, he found upon his desk a dictionary camouflaged to represent a cook-book; and also Miss Erith's complete report. And he lost no time in opening and reading the latter doc.u.ment: