Sandy did as requested, and then dropped to the floor with his
searchlight laid along the extension of the cord.

"The other end is loose!" he said in a tone of alarm.

"Loose?" echoed Tommy. "How did it ever get loose?"

Sandy sat down on the floor of the passage and began drawing the cord
in, hand over hand.

"I'm going to see if it's been cut!" he said.

Tommy stepped on the swiftly moving cord and held it fast to the
floor.

"You mustn't draw it in!" he exclaimed. "As long as it lies on the
floor as we strung it out, we can follow it without taking any
chances. If you pull it in, then it's all off."

"I understand!" Sandy agreed. "I didn't pull much of it in."

The boys started up the gangway, one of them keeping a searchlight on
the white thread of cord.

They seemed to make a great many turns and once or twice Sandy
declared that they were walking round and round in a circle.

"I don't believe the passages run so we could walk around in a
circle!" argued Tommy. "That ain't the way they run passages in