Ralph had both mind and hands full during the trip. As to Fogg, he went straight about his duties, grimly silent and mechanically. As the fire and vim of stimulation died down, Ralph could see that it was with the most exhaustive effort that his fireman kept up his nerve and strength. Fogg was weak and panting the last shovel full of coal he threw into the furnace, as they sighted Stanley Junction. He was as limp as a rag, and looked wretched as the train rolled into the depot. They ran the locomotive to the roundhouse. Ralph went at once to the foreman's office, while Fogg attended to the stalling of No. 999. He found the night watchman asleep there and no orders on the blackboard for Fogg or himself. This meant that they need not report before noon. Ralph looked around for the fireman when he came out of the office, but the latter had disappeared, probably headed for home. Ralph, half-across the turntable, halted and went over to No. 999. "The vest of that mysterious new acquaintance of mine, Clark--Porter," said Ralph--"he said he left it in the locomotive." Ralph did not find the article in question in his own bunker. He threw back the cover of Fogg's box, to discover the vest neatly folded up at the bottom of that receptacle. With some curiosity he looked over its pockets. "Whew!" whistled Ralph, as he removed and opened the only article it contained--a check book. The checks were upon a bank at Newton. About half of what the book had originally contained had been removed. Examining the stubs, Ralph calculated that over $1,000 had been deposited at the bank in the name of Marvin Clark, and that fully half that amount had been checked out. "This is pretty serious," commented the young engineer. "It looks as if the impostor has not only stolen Clark's name, but his passes and his check book as well. I don't like the looks of this. There's something here I can't figure out." Ralph placed the check book in his own pocket and returned the vest to the box. As he did this, he disturbed a piece of cloth used by Fogg to wipe grease from the cab valves. Something unfamiliar to the touch was outlined wrapped up in the rag, and Ralph explored. Two objects came into view as he opened the piece of cloth. With a great gasp the young engineer stared at these. Then he rolled up the rag and placed it and its contents in his pocket. His face grew grave, and Ralph uttered a deep sigh, startled and sorrowful. The young engineer of No. 999 had made a discovery so strange, so unexpected, that it fairly took his breath away. The mystery of the collision on the siding at Plympton was disclosed. CHAPTER IX THE LIGHT OF HOME Ralph walked home in the quiet night in a serious and thoughtful mood. His usually bright face was clouded and his head bent, as though his mind was greatly upset. As the light of home came into view, however, with a effort he cast aside all railroad and personal cares.