There, he crouched over the short-wave radio set and waited and listened. The air was alive with calls and messages. From time to time, he caught the reports from the three navy planes that were winging steadily on their flight after the Comerford.
Then, just after midnight, the reassuring words of the operator on one of the bombers were cut off short.
"They've struck the zone of silence," Curtis whispered. "The Comerford must have spread it, so that it encircles the entire convoy. Those bombers'll shove in, see what's happening and come back out of the zone to report, even if their radios are silenced. Nelson never figured on that!"
His telephone shrilled. It was Captain Rathbun, of the British Intelligence. His words confirmed Curtis' suspicions.
"I've just had word from Halifax. They arranged to contact the Carethusia's convoy by wireless every night at eleven-thirty, but tonight, they got no answer. The convoy must be caught in the zone of silence."
Curtis couldn't keep the note of triumph out of his voice. "Then all we've got to do is locate the convoy—and we've got the Comerford!"
"Cheerio!" said Rathbun's voice, and he hung up.
Curtis relaxed in his chair beside the short-wave set. Dawn came and found him still alert, listening, wakeful. He had breakfast sent up, but touched nothing except the pot of black coffee.
Several times, he computed the probable flying time of the three planes, and the distance the slow-moving convoy could have covered since sailing at midnight on the previous Friday. Then he tried to find the position of the convoy on the map.