Edgar Award for Best First Novel by an American Author. 

Dick Stoddard knew that he was suffering from a mild case of poisoning. It was the result of his job; he was head of a research team in a top-security chemical plant. 

He also knew that the mild poisoning might develop into panics, depressions, delusion, hallucination. "All these" said the doctor casually, "depended upon the individual's reaction."

One of Dick's associates, Steve Hakios, had been affected to such an extent that he had been force to abandon the work entirely. 

"Highly susceptible individual," said the doctor, and again Casually.

This work opens on the morning that Dick Stoddard came to the plant very early and found Steve There, alone and obviously very ill. 

Fifteen minutes later, he was no longer there. And it was impossible for dick to convince anybody that he had ever been there. 

The security guards had not seen him come in or leave; other key people in the building had not seen him. It was impossible for him to have been there. 

there was only one logical explanation: Dick himself, finally was having hallucinations. "I warned yo this might happen," said the doctor, this time sorrowfully. 

This is an extraordinary first novel--spare, tense, unrelenting in the pace, reminiscent of the mood of and suspense of The Lady Vanishes.