The question fell into absolute silence. Long afterward Susan was to remember the way Rosina’s strong, wide, white hand closed upon the dice and held them rigidly. And her own swift, queer recollection of the empty room upstairs. The room where a kind old man had been cruelly murdered.

She couldn’t have spoken. And Durrie, all at once white and strange, cried: “You thought you’d fasten it on Rosina. But she didn’t kill him. She—”

“Durrie,” said Miriam. “Don’t you know that only Rosina could have done it.”

Durrie leaped to his feet. Rosina did not move and neither did Miriam.

And in the silence they all heard the sudden squealing of the brakes of an automobile at the side of the house.

“Jim,” thought Susan. “Oh, let it be Jim—”

It was. Durrie went to the door and let him in. He gave one look at Susan and said very pleasantly that he’d come to take her home.

There was a bad moment when Miriam Wiggenhorn raised an objection.

“But you have only begun the investigation, Miss Dare. This is most distressing—most inconclusive—”

Jim said crisply: “Miss Dare will put any evidence she has into your hands in due form—”

It puzzled them a little. And in the instant of perplexity Jim thrust Susan out the door and closed it smartly behind them.

The engine of his car was running. Thirty seconds later they had turned into the public road and the Wiggenhorn house was a dark, brooding bulk behind them. “J-Jim,” said Susan shakily.

“Scared?”

“Terrified—”

His profile looked forbidding. He said grimly: “I got your message. Drove like hell. What have you been stirring up?”

“Oh,” said Susan. “A man was murdered, and I know who killed him. Can you remember chemistry?”

The car swerved, recovered, and Jim muttered. Susan went on:

“What was the name of that gas that’s so dangerous? To breathe, I mean. It’s heavier than air and if left open passes into the air. And when you transfer it from one container to another you have to be so careful not to breathe it—it burns the lungs or something.”

“Wait a minute. Let me pull myself together.” He lighted a cigarette and thought for a moment. “I know—you can see the fumes above the test tube. Otherwise you can’t detect its presence except by smell. And if the tube is on its side all the gas escapes into the air. I’ll remember it in a minute—hydrogen—”

“Hydrogen chloride,” said Susan.

“Somebody die of it?”

“I think so,” said Susan. “I’m sure—but somebody else can do the proving. I won’t. They’ll have to start with an autopsy.”

Jim said: “Begin at the beginning.”

Susan did. It took a long time and Jim said nothing till she had finished.