Birdie was more than a trifle scared. He did not fully understand what he was about to do--he could not possibly have had the foggiest inkling of the volcanic power that had been compressed into the few drachms of viscous yellow liquid which swilled about in the tiny phial on which his fingers rested. He had about as much chance of appreciating anything so vast as he had of comprehending the metaphysical conception of infinity. All he knew was that he was carrying a very small quantity of the most powerful explosive known to science--whatever that might mean. Thanks to his weedy frame, he had not had the experience of high explosives which was presented _gratis_ to some millions of men between the years of 1914 and 1918. All he knew about explosives was that they went off with a bang, and that they couldn't be so very terrible. Thinking things over, he was at a loss to account for the fear he had when his hand first touched that precautionary calorimeter. No; what scared Birdie now was the knowledge that he was about to commit a bigger crime than any in his petty, sneaking career. What he thought was that his boss had a grudge against Cardan, and that the mucid amber in the phial would simply injure the editor enough to make him sorry for whatever he had done to the Apex. Birdie hadn't any idea what size crime that might be, or how long a stretch he would get for it if he was caught, but he was sure that it would be something pretty nasty. Like a furtive shadow he began to quicken his steps so as to catch up with Cardan. One hand, resting in his pocket, held the copper ice-box steady, while his finger and thumb grasped the slim neck of the phial. It must be a quick job, and a quick getaway to follow--be the explosion ever so small, he was too well known to the splits to risk being seen loafing anywhere around when the bang happened. His fingers shook a little, and he strove to hold them still. It would be fatal to bungle during the couple of seconds the bottle would take to flash from the calorimeter to John Cardan's waistcoat pocket. By an effort of will he got his hand back to rock-like firmness and throttled down the twitching of his nerves, but he could not control the chilly perspiration which broke out on his palms. Nearer and nearer he drew, his shifty eyes on the alert for exactly the right combination of circumstances for the fatal movement. It came when they had nearly reached the law Courts--in the shape of three men who were approaching abreast. Birdie came level with Cardan at precisely the right moment, so that for a moment the five of them were in line, so close together that their shoulders brushed....