"What's the idea of this?"
"A clue," said Pillingshot. "See anything queer about it? See that rummy brown stain on it?"
"Yes."
"Blood!" snorted Pillingshot.
"What's the good of blood? There's been no murder."
Pillingshot looked serious.
"I never thought of that."
"You must think of everything. The worst mistake a detective can make is to get switched off on to another track while he's working on a case. This match is a clue to something else. You can't work on it."
"I suppose not," said Pillingshot.
"Don't be discouraged. You're doing fine."