rate, he waited for half an hour for her to come out
of the shop, and when she didn't appear he walked in and found there was
another entrance through which she had gone. Since then she has not been
back to the hotel."

"I don't like that," said Tarling, a little troubled. "I wished her to be
under observation as much for her own protection as anything else. I wish
you would keep a man at the hotel and telephone me just as soon as she
returns."

Whiteside nodded.

"I've anticipated your wishes in that respect," he said. "Well, what is
the next move?"

"I'm going to Hertford to see Miss Rider's mother; and incidentally,
I may pick up Miss Rider, who is very likely to have gone home."

Whiteside nodded.

"What do you expect to find out from the mother?" he asked.

"I expect to learn a great deal," said Tarling. "There is still a minor
mystery to be discovered. For example, who is the mysterious man who
comes and goes to Hertford, and just why is Mrs. Rider living in luxury
whilst her daughter is working for her living at Lyne's Store?"

"There's something in that," agreed Whiteside. "Would you like me to come
along with you?"

"Thanks," smiled Tarling, "I can do that little job by myself."

"Reverting to Milburgh," began Whiteside.

"As we always revert to Milburgh," groaned Tarling. "Yes?"

"Well, I don't like his assurance," said Whiteside. "It looks as if all
our hopes of getting a clue from the examination of Lyne's accounts are
fated to be dashed."

"There's something in that," said Tarling. "I don't like it myself. The
books are in the hands of one of the best chartered accountants in the
country, and if there has been any monkey business, he is the fellow
who is certain to find it; and not only that, but to trace whatever
defalcations there are to the man responsible. Milburgh is not fool
enough to imagine that he won't be found out once the accountants get
busy, and his cheeriness in face of exposure is to say the least
disconcerting."

Their little conference was being held in a prosaic public tea-room
opposite the House of Commons--a tea-room the walls of which, had they
ears, could have told not a few of Scotland Yard's most precious secrets.

Tarling was on the point of changing the subject when he remembered the
parcel of books which had arrived at the accountant's office that
morning.

"Rather late," said Whiteside thoughtfully. "By Jove! I wonder!"

"You wonder what?"

"I wonder if