Danny the Detective by Vera C. Barclay — Read

Four days after war was declared, on August 8th, a motor-bike dashed into the village, and from it jumped the District Commissioner. Before long, he, the Scoutmaster, and three of the Patrol-Leaders were shut into the Scout Headquarters; the Cubs hung about outside, longing to know what was on.

The Commissioner's news was that the War Office urgently called on Scouts to guard the trunk cable-line from being tapped or cut in a certain area, day and night, at once, until further orders. German spies were suspected of tampering with most important telegraph wires. Government secrets were getting out, wrong messages were coming through. Also, messages were somehow getting through to Germany.