father. "There are two men down there now signaling to the motorboat. We'd better go upstairs."
"Where does that lead to?"
"Outside. It will bring us into the shed near the house."
Fenton Hardy moved over toward the door.
"We haven't any time to lose," he said. "I have the revolver. If we meet any one—"
He opened the door cautiously and peeped out. There was no one beyond. There was nothing but a flight of steps leading upward into darkness.
The detective went forward, his sons following close at his heels.
Step by step they made their way on up in the darkness, for Joe had closed the door behind them and Frank did not dare make use of the flashlight.
At last Fenton Hardy came to a stop. He was fumbling at something immediately above.
Then the boys saw a faint opening which grew larger above them and resolved itself into a square of grey light against which the head and shoulders of their father were fully silhouetted. Fenton Hardy had raised the trapdoor that concealed the entrance to the underground caves and passages.
Mr. Hardy looked out carefully. There was
