"Tell then and I give you a thousand pounds."
"Not good enough," said Burgh coolly, "see here, you let us go free and tell us the fan's secret, and I'll tell you."
"Yes, and get the fan, and learn the secret," cried Tung-yu excited, "but you cannot make use of the secret."
"Don't want to. And as to the fan, you can get it from the person I tell you of. Then you can fork out fifteen thousand."
The Chinaman deliberated. "We have been wrong about Major Tidman, I think," said he politely. "It seems someone else has it. I suppose----"
"I didn't kill the old girl myself if that's what you mean."
"Quite so," said Tung-yu, after another pause. "Well, as you can't make any use of the secret I'll tell you of it. Then you can go free, after you have told me who killed Miss Wharf."
"Eight oh," said Clarence, and Rupert listened breathlessly.
"The fan," said Tung-yu, "is jade on one side, and enamel on the other. The enamelled side is painted with a picture invisibly. To bring out the picture, this fan has to be waved in certain smoke--"
"What sort of smoke?"