He held up a large steel key of complicated structure.
"Why," exclaimed Dunlap surprised, "that looks like the key to the Exchange Place door. Where did you find it?"
"In the gutter, near the sewer opening at the corner."
"But how did it get there?" asked Dunlap anxiously.
"Perhaps I shall be able to answer that question presently," said Sturgis. "Shall we go in now? No, not that way. Let us enter by the Wall Street side, if you please."
A couple of minutes later, the outer door of the Knickerbocker bank was unlocked.
"Excuse me if I pass in first," said Sturgis, entering. "I wish to see something here."
He bent low over the tiled entrance, with the magnifying glass in his hand.
"It is too bad," he muttered to himself presently. "They have trodden all over the trail here. Ah! what is this?"
"What?" inquired Dunlap.