* * * * * Lance glanced at his watch. Nine-thirty. The torpedoes were even now on their way, hurtling along miles above the earth. In fifteen minutes they would be over San Francisco. In fifteen minutes the Singe beacon had to meet them. He was not familiar with the Slav plane's instruments, but he judged he'd traveled some hundred and twenty-five miles; was nearing the outskirts of San Francisco. The air below would be thick, probably, with enemy scouts, but his appearance should pass unchallenged as long as they didn't glimpse his betraying uniform. He set the plane's nose down in a long slanting dive. Whipping through the clouds, the guarding search-rays of San Francisco were soon visible. Lance saw a few patrols of enemy scouts; he clung to the clouds, decreased his speed, and began circling over the heart of the metropolis itself. Twenty to ten. Occasionally a Slav plane flashed by him. Thank God, they didn't challenge! Lance went still lower. Finally, at a thousand feet, he set the helicopter props in motion and hung in mid-air--directly above the very center of the city. Sixteen minutes to ten. Now! * * * * * In the American front-line trenches, massed troops crouched expectantly. Clustered on every air base were flights of planes, each one crammed with bombs. Far behind, the Yank gun-crews edged nervously up to their mighty charges, and fingered anxiously the stubby gas shells which soon would be flung through the dripping night. And at Base No. 5 a very uneasy Colonel Douglas paced back and forth in his office, muttering: "No news from Lance! No news from Lance! God! He can't have failed! But why doesn't he show up?" He had not failed. Hovering in the plane over San Francisco Lance squirmed round in his seat, reached back into the fuselage, and pressed rapidly the studs on the Singe beacon. A high whining noise pierced instantly through the plane. And up stabbed the beacon, invisible, deadly--up, up, up to a thin realm miles above, where it flashed into an awesome squadron of terrible shells of steel! Shells that, a second later, wavered, staggered, and plunged earthward! And Lance tensed in his seat. From above, he caught a tiny whistling noise--a whistling that hurtled into a terrific shriek--that roared ever closer. "Carry on!" he muttered. "Carry on!" The words froze on his lips, for the world was suddenly consumed, it seemed, by flame and splitting, bellowing thunder. * * * * * The American guns spoke. From every aerodrome long flights of scouts and bombers and transport planes roared upward. In the front trenches the troops, still somewhat dazed by the earth-shaking explosion that had just tumbled from the far horizon--a horizon still lit by leaping tongues of awful flame--poured over the top, gas-masks on, repeaters and portable machine-guns at the ready, with a fierce cry on their lips.