false scent."

At Cape Charles the pilot swung east over Chesapeake Bay. Hardly had
he turned than Dr. Bird gave a cry. Excitedly he pointed toward the
water. Carnes grasped a pair of binoculars and looked in the
direction Dr. Bird was indicating. Sliding along under the water was
a long cigar-shaped shadow.

"It's a submarine!" exclaimed Carnes. "Is it a navy ship or the one
we're after?"

"It's no navy sub," said the doctor positively. "It's not the right
shape. Look at that bump on the side!"

The symmetry of the craft was marred by a huge projection on one side
that could not be explained by the pattern of any known type of
under-water craft.

"He's towing the borer!" cried the doctor in exultation. He took up
the speaking tube. "Turn back to sea!" he cried. "We passed four
destroyers less than ten miles out. We want to get in touch with
them."

The plane roared out to sea while Dr. Bird feverishly sounded the
"Alnav" call on the radio sending set. In a few minutes an answer
came. From their point of vantage they could see flags break out at
the peak of the destroyer leader. The four ships turned into column
formation and stormed at full speed into the bay. The plane raced
ahead to guide them.

"We've got him this time, Doctor!" cried Carnes in exultation. He
pointed to the bay below where the submarine was still making its way
slowly forward. Dr. Bird shook his head.

"I hope so," he said, "but I have my doubts. Saranoff is no fool. He
wouldn't walk into a trap like this unless he had some means of
escape. Here comes the first destroyer. We'll soon know the truth."

* * * * *

With the radio set he directed the oncoming boat. The destroyer
reduced to half speed and changed direction slightly. From side to
side she maneuvered until she was less than half a mile behind the
submarine and headed straight for it. Dr. Bird tapped a few words on
his key. With a belch of smoke, the destroyer lurched forward. She
cut the waters with her sharp bow, throwing up a wave higher than her
decks. Dr. Bird watched anxiously.

The destroyer was almost over the submarine and Dr. Bird's fingers
trembled on the key. One word from him would send a half dozen depth
charges into the water. On came the destroyer until it was directly
over the underseas craft. Dr. Bird pounded his key rapidly.

"Good Lord!" cried Carnes.

From the bump on the side of the submarine came a flash of red light.