Instantly his alert brain grasped the significance of the discovery. He connected it immediately with a message he had received from Hilton some days previously, referring to the suspicious characters hanging about the vicinity of the Manor, and to the fear that an attempt might be made to steal the boat. At the time he had dismissed the idea as absurd, but now----! Without further scruple, he proceeded to make himself master of the contents of the letter. It was brief, but very much to the point, running thus: “DEAR FRIEND AND COLLEAGUE,--It is imperative that the affair be carried out without delay, as we are advised that the expedition starts within two days. Once the vessel leaves the dock, not all the plotting in the world could ever give us possession of her. Therefore it remains for you, my friend, to carry out your part of the programme with all speed. You must gain possession of the submarine to-night. Let nothing hinder you. We hear that Hilton Manor is a lonely house, and four determined men, well armed, should be able to overcome all resistance offered by the inventor and his friends. What matter a few lives more or less, so that our plan succeeds and we attain our object? The _Night Hawk_ will await you at the appointed spot, outside the bay. _We remind you of the penalty of failure!”_ That was all, but it was enough to startle even the cool-blooded Yankee for a moment. The missive was practically the death-warrant of his friends down at Hilton, who were even now preparing for departure on their North Polar trip. Hastily he placed the incriminating sheet in his breast pocket, wondering the while why the conspirators had left the train, instead of going straight through to Stanwich. Hardly had the thought crossed his mind ere the twain reappeared, and climbed into the carriage. Haverly noted with secret satisfaction that they seemed strangely uneasy, glancing about as though searching for something. “Lost anything?” he inquired casually, as the train moved off again. “No,” one of them snarled, but the look with which he favoured the American made that gentleman glad that he carried a six-shooter in his pocket. Ere long the express was once more racing over the country at sixty miles an hour. The millionaire’s scoundrelly companions seemed by this time to have given up their search, for they settled themselves back against the cushions, muttering together in low tones, which the roar of the train completely drowned. Haverly, whilst apparently studying the flying landscape, contrived to keep his eye upon the pair, who had evidently made up their minds that their fellow-traveller had picked up their lost letter. At length one of them addressed the American. “Could you oblige me with a match?” he asked. He produced a cigar-case as he spoke, and extracted one of the three cigars within.