"Who shot her?" cried Rogers as he rushed into the hospital three minutes after his ex-wife died from a bullet through her head.

"Just a minute, Mr. Rogers," said Professor Stiggins. "We'll have to ask you a few questions-routine, you know. Although divorced for the past six months, you have been living in the same house with your ex-wife, have you not?"

"That's right," replied Rogers.

"Had any trouble recently?"

"Well, yesterday, when I told her I was going on a business trip, she threatened to commit suicide. In fact, I grabbed a bottle of iodine from her as she was about to drink it. When I left last evening at seven, however, telling her I was spending the night with friends in Sewickley, she made no objection. Returning to town this afternoon," continued Rogers, "I called my home and the maid answered."

"Just what did she say?" inquired Stiggins.

"'Oh, Mr. Rogers, they took poor mistress to St. Ann's Hospital 'bout half an hour ago. Please hurry to her.'
"She was crying, so I couldn't get anything else out of her; then I hurried here. Where is she?"

"The nurse will direct you," said Stiggins with a nod.

"A queer case, this, Professor," said Inspector Kelley. "These moderns are a little too much for me, I'm afraid. A man and woman living together after being divorced six months!"

"A queer case indeed, Inspector," mused the professor, "and you'd better detain Mr. Rogers. If he didn't shoot her himself, I'm confident he knows who did."

Why did the professor advise the Inspector to detain Rogers?