While Bothwell was watching the builder's men upon the green hill beside the Atlantic, Edward Heathcote was slowly, patiently, laboriously following the thin thread of circumstantial evidence which was to lead him to the solution of Léonie Lemarque's fate. He had taken this task upon himself in purest chivalry, an uncongenial duty, entered upon in unselfish devotion to the woman he loved. He pursued it now with a passionate zest, a morbid interest, which was a new phase in his character. Never had he followed the doublings of some cunning old dog-fox across the moors and heaths of his native land with such intensity as he followed that unknown murderer of Léonie Lemarque. That she had been murdered--deliberately sacrificed--as the one witness of a past crime, was now his conviction. He had ceased to halt between two opinions. Léonie had gone to meet the murderer of her aunt, and she had fallen a victim to the folly of the dying woman who had sent her to seek protection from such a source. Who was that murderer, and for what reason had he carried his helpless prey to a remote Cornish valley? Why should he not have tried to get rid of her in the great wilderness of London, where the crime would have excited much less curiosity, and would have been less likely to be discovered? Entering deliberately into the thoughts of the assassin, following out the working of his mind, his fears, his calculations, his artifices, it seemed to Heathcote that a man familiar with the line between Plymouth and Penzance might scheme out just such a murder as that which had been committed, might fix on the very spot at which the deed was to be done, knowing that at that particular point the palisades had been removed, and the viaduct left unprotected. He would speculate that the fall of a strange girl at such a spot would be accepted as purely accidental. He would trust to his own cleverness for finding the way to disconnect himself from the catastrophe; he would imagine that in the hurry and confusion following such an event it would be impossible for the murderer to be identified. Who was to select from all the travellers in a train that one traveller whose arm had thrust the girl to her doom? A little cleverness and watchfulness on his part would render such identification impossible. A man provided with a railway key could get from one carriage to another easily enough, in the surprise and horror of the moments following upon the girl's fall. Few men are quite masters of their senses during such moments, and all eyes would be turned towards the gorge at the bottom of which the girl was lying; everybody's thought would be as to whether she was living or dead. Very easy in such a moment for an active man to pass from one carriage to the other, unobserved by any creature in or about the train.