be the devil to pay. Of course all these envelopes were first opened
in my office. It takes a dozen years to train men to open sealed
envelopes so that neither flap nor seal is broken, and both can be
again secured without showing a sign of disturbance. It is a trade
secret."

Dawson's expert fingers then opened the twelfth envelope, and he
produced a letter. "Now, Mr. Cary, if we had not known you and also
known that you were absolutely honest and loyal--though dangerously
simple-minded and careless in the matter of windows--this letter would
have been very awkward indeed for you. It runs: 'Hagan arrives 10.30
p.m. Wednesday to get Cary's Naval Notes. Meet him. Urgent.' Had we
not known you, Mr. Richard Cary might have been asked to explain how
Hagan knew all about his Naval Notes and was so very confident of
being able to get them."

Cary smiled. "I have often felt," said he, "especially in war-time,
that it was most useful to be well known to the police. You may ask me
anything you like, and I will do my best to answer. I confess that I
am aghast at the searchlight of inquiry which has suddenly been turned
upon my humble labours. My son at sea knows nothing of the Notes
except what I have told him in my letters, my wife has not read a line
of them, and my publisher is the last man to talk. I seem to have
suddenly dropped into the middle of a detective story." The poor man
scratched his head and smiled ruefully at the Scotland Yard officer.

"Mr. Cary," said Dawson, "those windows of yours would account for
anything. You have been watched for a long time, and I am perfectly
sure that our friend Hagan and his associates here know precisely in
what drawer of that desk you keep your Naval Papers. Your flat is easy