ound and said even walls had ears."

"Maybe she meant a dictaphone," said Julius with interest.

"Miss Tuppence is right," said Sir James quietly. "We must not leave the
flat--if only for Mrs. Vandemeyer's sake."

Julius stared at him.

"You think he'd get after her? Between now and to-morrow morning. How
could he know, even?"

"You forget your own suggestion of a dictaphone," said Sir James dryly.
"We have a very formidable adversary. I believe, if we exercise all due
care, that there is a very good chance of his being delivered into our
hands. But we must neglect no precaution. We have an important witness,
but she must be safeguarded. I would suggest that Miss Tuppence should
go to bed, and that you and I, Mr. Hersheimmer, should share the vigil."

Tuppence was about to protest, but happening to glance at the bed she
saw Mrs. Vandemeyer, her eyes half-open, with such an expression of
mingled fear and malevolence on her face that it quite froze the words
on her lips.

For a moment she wondered whether the faint and the heart attack had
been a gigantic sham, but remembering the deadly pallor she could hardly
credit the supposition. As she looked the expression disappeared as by
magic, and Mrs. Vandemeyer lay inert and motionless as before. For a
moment the girl fancied she must have dreamt it. But she determined
nevertheless to be on the alert.

"Well," said Julius, "I guess we'd better make a move out of here any
way."

The others fell in with his suggestion. Sir James again felt Mrs.
Vandemeyer's pulse.

"Perfectly satisfactory," he said in a low voice to Tuppence. "She'll be
absolutely all right after a night's rest."

The girl hesitated a moment by the bed. The intensity of the expression
she had surprised had impressed her powerfully. Mrs. Vandemeyer lifted
her lids. She seemed to be struggling to speak. Tuppence bent over her.

"Don't--leave----" she seemed unable to proceed, murmuring something
that sounded like "sleepy." Then she tried again.

Tuppence bent lower still. It was only a breath.

"Mr.--Brown----" The voice stopped.

But the half-closed eyes seemed still to send an agonized message.

Moved by a sudden impulse, the girl said quickly:

"I shan't leave the flat. I shall sit up all night."

A flash of relief showed before the lids descended once more. Apparently
Mrs. Vandemeyer slept. But her words had awakened a new uneasiness in
Tuppence. What had she meant by that low murmur: "M