“Can’t you guess,” said the detective, “No? Yet you saw that rainwater cistern?”
“Yes.”
“And you observed that the walls of the tank were wet almost up to the top?”
“I did.”
“Yet there was only a foot of water in the cistern, in spite, of the fact that it has rained continuously since Wednesday night.”
“That is curious, certainly.. But what does it point to?”
“It points to the fact that that cistern has recently been emptied.”
“But how, and by whom?”
Sexton Blake shrugged his shoulders.
“You’re very dense,” he said. “This drift apparently runs under Mr. Verrill’s house. Suppose a man were working in this drift yesterday morning, blasting the rock in search of jet. Suppose that, in the course or his blasting operations, he blasted a hole in the floor of Mr. Verrill’s rainwater tank
