In fact, she was one of those girls who unintentionally and innocently render masculine minds uneasy through some delicate, indefinable attraction which defies analysis.

“Surely,” murmured the D. C., “surely!  Hum—­hum!”

A subtle freshness like the breath of spring in a young orchard seemed to linger about her.  She was exquisitely fashioned to trouble men, but she didn’t wish to do such a—­

Vaux, who was in love with another girl, took another uneasy look at her, sideways, then picked up his unlighted cigar and browsed upon it.

“Yes,” he said nervously, “this is one of those accursed code-ciphers.  They always route them through to me.  Why don’t they notify the five—­”

“Are you going to turn this over to the Postal Inspection Service?”

“What do you think about it, Miss Erith?  You see it’s one of those hopeless arbitrary ciphers for which there is no earthly solution except by discovering and securing the code book and working it out that way."7

She said calmly, but with heightened colour: 

“A copy of that book is, presumably, in possession of the man to whom this letter is addressed.”

“Surely—­surely.  Hum—­hum!  What’s his name, Miss Erith?”—­glancing down at the yellow envelope.  “Oh, yes—­Herman Lauffer—­hum!”

He opened a big book containing the names of enemy aliens and perused it, frowinng.  The name of Herman Lauffer was not listed.  He consulted other volumes containing supplementary lists of suspects and undesirables—­lists furnished daily by certain services unnecessary to mention.

“Here he is!” exclaimed Vaux; “—­Herman Lauffer, picture-framer and gilder!  That’s his number on Madison Avenue!”—­pointing to the type-written paragraph.  “You see he’s probably already under surveillance-one of the several services is doubtless keeping tabs on him.  I think I’d better call up the—­”

“Please!—­Mr. Vaux!” she pleaded.

He had already touched the telephone receiver to unhook it.  Miss Erith looked at him appealingly; her eyes were very, very hazel.

“Couldn’t we handle it?” she asked.

“We?”

“You and I!”

“But that’s not our affair, Miss Erith—­”

“Make it so!  Oh, please do.  Won’t you?”

Vaux’s arm fell to the desk top.  He sat thinking for a few minutes.  Then he picked up a pencil in an absent-minded manner and began to trace little circles, squares, and crosses on his pad, stringing them along line after line as though at hazard and apparently thinking of anything except what he was doing.

The paper on which he seemed to be so idly employed lay on his desk directly under Miss Erith’s eyes; and after a while the girl began to laugh softly to herself.

“Thank you, Mr. Vaux,” she said.  “This is the opportunity I have longed for.”

Vaux looked up at her as though he did not understand.  But the girl laid one finger on the lines of circles, squares, dashes and crosses, and, still laughing, read them off, translating what he had written: