“It’s my heart,” she whispered.  “I mustn’t talk.”

She lay back with closed eyes.

Sir James kept his finger on her wrist a minute longer, then withdrew it with a nod.

“She’ll do now.”

All three moved away, and stood together talking in low voices.  One and all were conscious of a certain feeling of anticlimax.  Clearly any scheme for cross-questioning the lady was out of the question for the moment.  For the time being they were baffled, and could do nothing.

Tuppence related how Mrs. Vandemeyer had declared herself willing to disclose the identity of Mr. Brown, and how she had consented to discover and reveal to them the whereabouts of Jane Finn.  Julius was congratulatory.

“That’s all right, Miss Tuppence.  Splendid!  I guess that hundred thousand pounds will look just as good in the morning to the lady as it did over night.  There’s nothing to worry over.  She won’t speak without the cash anyway, you bet!”

There was certainly a good deal of common sense in this, and Tuppence felt a little comforted.

“What you say is true,” said Sir James meditatively.  “I must confess, however, that I cannot help wishing we had not interrupted at the minute we did.  Still, it cannot be helped, it is only a matter of waiting until the morning.”

He looked across at the inert figure on the bed.  Mrs. Vandemeyer lay perfectly passive with closed eyes.  He shook his head.

“Well,” said Tuppence, with an attempt at cheerfulness, “we must wait until the morning, that’s all.  But I don’t think we ought to leave the flat.”

“What about leaving that bright boy of yours on guard?”

“Albert?  And suppose she came round again and hooked it.  Albert couldn’t stop her.”

“I guess she won’t want to make tracks away from the dollars.”

“She might.  She seemed very frightened of ‘Mr. Brown.’ "

“What?  Real plumb scared of him?”

“Yes.  She looked round 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.