so closely that he could not escape--and evidently he
couldn't." A moment later Captain Hardy stood frowning, trying to
puzzle out the meaning of it. "I don't see how he could have sent a
message," he continued, "if he is so closely watched that he couldn't
get away."

"Perhaps the message will tell us," suggested Roy.

"Right again, Roy," said Captain Hardy. "We'll hurry to the office and
decipher it."

On the run they made their way to the subway station at Bowling Green.
They caught a north bound train and shortly afterward swarmed up out of
the subway and made a rush for the secret service offices.

With hardly more than a word of greeting they drew up at a table and
laid the paper with the message before them.

"Forty," said Captain Hardy, counting the letters. "If they use the
same cipher they did last time, that'll make five columns of eight
letters each." Rapidly he set down the letters in the order indicated,
thus:

T T E N R
H A S E Y
G Y U R A
I L O E B
N T V R O
D C Z E H
I A E V C
M X D E E

Then slowly he read off the message:
"ECHO--BAY--REVERE--RENDEZVOUS--EXACTLY--AT--MIDNIGHT."

With a cry of joy Captain Hardy leaped to his feet. "We've got another
chance," he said. "Sanders must be going to meet them at Revere
Rendezvous--wherever that is." Then, turning to a man at the next
desk, he inquired, "Where is Echo Bay?"

"At New Rochelle," said the agent. "That's where Fort Slocum is."

"Fort Slocum!" cried Captain Hardy. "This may be even more serious
than it seems. Can this man be spying on the fort, too? How far is
New Rochelle from here?"

"Eighteen or twenty miles."

"Can we get there by twelve o'clock?"

"Sure. Why?"

"The spies we are after are to meet at Echo Bay, Revere Rendezvous, at
midnight. Are you sure that we can get there?" Then he glanced at his
watch. "It's already long past ten."

The Chief was still at the office. The agent went to consult him, and
came back for details. Captain Hardy stepped into the Chief's private
office and made the entire situation plain. The Chief sat like a cake
of ice, a thinking machine immovable and unmoved, listening to the
recital.

"How many men have you here?" he asked his subordinate, the instant
Captain Hardy had done talking.

"Four."

"Two of you go by automobile, two by motorboat. Divide these boys and
take half with each party. Let those who go by land approach the
meeting-place on