"But it did happen," the Sergeant pointed out.
"Yes, that's what makes me wish I'd never joined the Force," said Hemingway. He walked into the bathroom, and gazed up at the ventilator. "If that was the only thing open, and they're all agreed it was, it looks as though it has a very important bearing on the case. Hand me that stool, will you?"
The Sergeant brought the cork-topped stool to him, and he climbed on+to it, to inspect the ventilator more closely.
"If anyone got in that way, he'd have had to be a small man," said Ware. "The young fellow we saw downstairs couldn't have done it."
"No one could have got in without scratching the paint with his shoes."
"Rubber soles," suggested the Sergeant.
"You may be right. Assume someone did get in this way. How?"
"I was thinking he might have climbed up by a ladder.
There's bound to be one in the gardener's shed, for pruning the fruit trees."
"That doesn't interest me. What I want to know is, how did he set about oozing through this highly improbable aperture once he had climbed up the ladder?"