"We went beyond our depth," said Harry, when they reached New York. "The game was too hard to solve. The mystery of the murdered man in the box must remain unsolved. It can go on record as one of the many strange cases that have baffled the detectives before. It's our duty now to report the matter to our chief, drop it, and resume our attempt to locate the broker's mail thief."
"Then come to headquarters at once," said Old King Brady, as they left the cars.
They met the chief in his office and he smiled pleasantly, and asked:
"Well, where have you two been keeping yourselves hidden during the past week? I haven't seen or heard from you lately."
The Bradys told him what they had been doing.
He listened attentively, with a grave look upon his face, while they were giving him the facts, and said when they finished:
"Then that murder mystery was too much for you, and you went beyond your depth trying to solve it, eh? Well, it's just as well you let it drop."
"Anything new going on?"
"Yes. Something relating to your mail robbery case."
"Indeed! What was it?"