"If I die of heart failure you will be responsible!" fiercely grated Scotch. "Doie!" cried Barney. "Whoy, ye'll live ter pick daisies on yer own grave, profissor." "This is terrible!" faintly rumbled the little man, as he regained his chair, and began to mop cold perspiration from his face with a handkerchief. There was a knock at the door. "Come in," cried Frank. The door opened, and a boy about seventeen years of age entered the room. He was a slender, delicate-appearing fellow, but he had a good face and steady eyes. "Hurrah!" cried Frank. "Here is my preserver! Professor Scotch, permit me to introduce you to Mr. Walter Clyde." The professor held out a limp hand to the boy, saying: "Excuse me if I do not rise. Frank just robbed me of strength by telling how you saved his life by derailing an express train and killing forty passengers." Clyde was quick to catch on. A faint look of astonishment was followed by a smile, and he said: "Mr. Merriwell is mistaken." "Ha!" cried the professor. "Then you denounce the whole story as false?" "I said Mr. Merriwell was mistaken--but thirty-nine passengers were killed," said the newcomer, who had caught the end of Frank's yarn. The professor came near having a fit, and Barney Mulloy held onto his sides, convulsed with merriment. "I beg your pardon, Mr. Clyde," said Frank. "I may have stretched the yarn a trifle." "Just a trifle!" muttered the professor. "If I had used giant-powder instead of dynamite in blowing up the track," said Clyde, "it is possible there might have been a smaller loss of life." "But you did not blow up the track at all," hastily put in Frank. "You yanked the train off the rails with a lasso." "So I did! I was thinking of another case. In this instance, if I had not stood so far from the railroad----" "But you were on the pilot of the engine." "Was I? So I was. Excuse me if I do not attempt any further explanations." Then the three boys laughed heartily, and the professor was forced to join in at last. Having restored Scotch to good nature, Frank requested Walter Clyde to tell his story. Clyde's face clouded a little, and he slowly said: "I will tell it briefly. Years ago, when I was a very small child, my father left his home in the East to make a trip to California. Business called him out there, and, on his way, he entered this Territory. He never reached California. "My father had a deadly enemy--a man who had sworn to kill him some day. That man's name was Uric Dugan. Father had been instrumental in sending him to prison for robbery, but he had escaped, fled to the West, and, it was said, joined the Mormons. "Fate led Uric Dugan and my father to meet in Utah. What happened then is known to Dugan alone. Months passed, and mother heard no word from father. She grew thin and pale and desperate. At length, a letter came to her. It was from Uric Dugan.