“That’s Driscoll, all over,” he said.  “Put him on a case, and he don’t say much, and he don’t look like he’s doing anything, and then all in a minute he’ll bring in the goods.”

“I’d be glad to hear the cause of that death,” said Dr. Crowell, musingly.  “I’m an old, experienced practitioner, and I’ve never seen anything so mysterious.  There’s absolutely no trace of any poison, and yet it can be nothing else.”

“Poison’s a mighty sly proposition,” observed Shane.  “A clever poisoner can put over a big thing.”

“Perhaps your assumption of murder is premature,” said Hendricks, and he gave Shane a sharp look.

“Maybe,” and that worthy nodded his head.  “But I’m still standing pat.  Now, here’s the proposition.  Three people, locked into a suite—­you may say—­of three rooms.  No way of getting in from this side—­those locks are heavy brass snap-catches that can’t be worked from outside.  No way, either, of getting in at the windows.  Tenth-story apartment, and the windows look straight down to the ground, no balconies or anything like that.  Unless an aryoplane let off its passengers, nobody could get in the windows.  Well, then, we have those three people shut up alone there all night.  In the morning one of ’em is dead —­poisoned.  What’s the answer?”

He stared at Eunice as he talked.  It was quite evident he meant to frighten her—­almost to accuse her.

But with her strange contradictoriness, she smiled at him.

“You have stated a problem, Mr. Shane, to which there can be no answer.  Therefore, that is not the problem that confronts us.”

“Fine talk—­fine talk, lady, but it won’t get you anywhere.  To the unbiased, logical mind, the answer must be that it’s the work of the other two people.”

“Then yours is not a logical or unbiased mind,” Hendricks flared out, “and I object to your making implications.  If you are making accusations, do so frankly, and let us know where we stand I If not, shut up!”

Shane merely looked at him, without resenting this speech.  The detective appeared to be marking time as he awaited the return of his partner.

And Driscoll returned, shortly.  His manner betokened success in his quest, whatever it may have been, and yet he looked distressed, too.

“It’s a queer thing,” he said, half to himself, as he fell into a chair Shane pushed toward him.  “Mrs, Embury, do you keep an engagement book?”

“Why, yes,” replied Eunice, amazed at the question put to her.

“Let me see it, please.”

Eunice went for it, and, returning, handed the detective a finely bound volume.

Hastily he ran over the dates, looking at notes of parties, concerts and theatres she had attended recently.  At last, he gave a start, read over one entry carefully, and closed the book.

Abruptly, then, he went back to Embury’s room, asking Dr. Crowell to go with him.