The telescribe bell announced another message. It found Irene sitting at the table in the instrument room with ordnance maps around her and the index book of the League's most trusted agents lying open on the shelf. She just glanced at the clock as she jumped up. It was 4.15, exactly the last minute of the half-hour that she had fixed as the limit of uncertainty. The message might even yet be from Salt. But it was not; it was this instead: "Fear Mr Salt has been arrested. He is in his motor-car, handcuffed, proceeding towards Guildford, in charge of man who has appearance of belonging to police force. Driver is not Mr Salt's man. Mr S. made opp. for me to see sit., but said nothing. Passed just W. of Puttenham 3.55. Roads good, but snow beginning. Car trav only 10-12 m. hour. Shall remain here on chance being use. Don't hesitate." A hall-formed plan was already floating in the space between Miss Lisle's adventurous brain and the maps. The Puttenham message crystallised it. There was now something to go on. The route she knew already; the times and mileages also lay beneath her hand. The scheme had a hundred faults, and only one thing to recommend it--that it might succeed. For ten minutes she flung herself into the details of the maps, jotting down a time, a distance, here and there a detail of the road. "Puttenham" might remain at his box till dawn, but all the work, all the chance, was forward--before the car. At the end of ten minutes Irene picked up the accumulation of her labours and rang up the telephone exchange. * * * * * "What is it, Murphy?" demanded the inspector through the tube, as the car came to a dead stop. "Something else in the way?" "I can't quite make it out, sir," was the reply. "We're just outside the long railway arch, and there seems to be something on fire towards the other end. Terrible lot of smoke coming through." "Can't we run up to it?" "This is an unusually long bridge--fifty or sixty yards, I should say. I hardly like to take you on into that smoke, sir." "Oh, very well. Jump down and see what it is. Only be as sharp as you can."