Bell was watching in deep admiration of the strong hand that was yet light as thistledown. The big electric light flickered for just a moment, and Heritage stood upright. "Don't be a fool," Bell said, sternly. "It's a mere matter of current." Heritage muttered that it must be. Nevertheless it had given him quite a turn. His face was set and pale and his hand shook ever so slightly. The knife was cutting deep, deeper-- A snarling oath broke from Bell's lips as the light flickered again and popped out suddenly, leaving the whole room in intense darkness. Heritage cried aloud. David felt a hand guiding his fingers to the patient's head. "Press the sponge down there and press hard," Bell whispered. "It's a matter of life and death. Another minute and Van Sneck would have gone. Heritage, Heritage, pull yourself together. It was no fault of yours the light went out--the fault is mine." Bell stumbled down the kitchen stairs and returned with a candle. The electric lights were out all over the ground floor with the exception of the hall. One of the circuits had given out completely, as sometimes happens with the electric light. Bell leapt on a table and turned the hall light out. A second later and he was dragging the long spare flex from the impromptu operating-room to the swinging cord over the hall lamp. With a knife he cut the cord loose, he stripped the copper wires beneath, and rapidly joined one flex to the other. "It's amateur work, but I fancy it will do," he muttered. "Anyway, that rascal is powerless to interfere with the circuit that controls the hall light." Snap went the hall switch--there was a sudden cry from Heritage as the big lamp over the head of Van Sneck flared up again. Bell raced into the study and shut the door. "A trick," he gasped. "The light was put out. For Heaven's sake, Heritage, don't get brooding over those fancies of yours _now._ I tell you the thing was done deliberately. Here, if you are too weak or feeble, give the knife to _me_." The request had a sting in it. With an effort Heritage pulled himself together. "No," he said, firmly, "I'll do it. It was a cruel, dastardly trick to play upon me, but I quite see now that it _was_ a trick. Only it's going to make a man of me instead." Bell nodded. His eyes were blazing, but he said nothing. He watched Heritage at work with stern approval. Nothing could have been more scientific, more skilful. It seemed a long time to David, looking on, but it was a mere matter of minutes. "Finished," Heritage said, with a triumphant thrill. "And successful." "And another second would have seen an end of our man," Bell said. "He's coming round again. Get those bandages on, Heritage. I'll look after the mess. Give him the drug. I want him to sleep for a good long time." "Will he be sensible to-morrow?" David asked.