"Did you travel with that woman Dexter to-night?" he inquired eagerly in a low whisper as they stood in the darkness. "Yes." "Did she carry her attache-case?" "Yes. She always does." "She did not have it when she went home yesterday morning, for she left it here--the case which your father prepared," he said. "She brought the second of the cases with her to-night." "Then both are here!" exclaimed Ella in excitement. "Both are now in the power-house. I saw her hand over the second one to Cole only a quarter of an hour ago. Let us watch." Then the pair crept on beneath the dark shadows through the rain to the great square building of red-brick which, constructed six months before, contained some of the finest and most up-to-date electrical plant in all the world. At last they gained the door, which stood slightly ajar. The other mechanics were all away in the canteen having their early morning meal, and the man Cole, outwardly an honest-looking workman, remained there in charge. Together they watched the man's movements. Presently he came to the door, opened it, and looked eagerly out. In the meantime, however, Kennedy and his companion had slipped round the corner, and were therefore out of view. Then, returning within, Cole went to a cupboard, and as they watched from their previous point of vantage they saw him unlock it, displaying the two little leather attache-cases within. Close to the huge main dynamo in the centre of the building there stood on the concrete floor six cans of lubricating-oil which, it was proved afterwards, were usually kept at that spot, and therefore were in no way conspicuous. Swiftly the man Cole drew a coil of fine wire from the cupboard, the ends being joined to the two attache-cases--so that if the mechanism of one failed, the other would act--and with quick, nimble fingers he joined the wire to that already attached to the six inoffensive-looking cans of "oil." The preparations did not occupy more than a minute. Then, seizing a can of petrol, he placed it beside the cans of high-explosive, in order to add fire to the explosion. Afterwards, with a final look at the wires, and putting his head into the cupboard, where he listened to make certain that the clockwork mechanism was in motion, he glanced at the big clock above. Then, in fear lest he should be caught there, he ran wildly out into the darkness ere they were aware of his intention. "Quick!" shouted Kennedy. "Rush and break those wires, Ella! I'll watch him!" Without a second's hesitation, the girl dashed into the power-house and frantically tore the wires from the cupboard and from the fastenings to the deadly attache-cases, and--as it was afterwards proved--only just in time to save herself, the building, and its mass of machinery from total destruction. Meanwhile, Kennedy had overtaken the man Cole, and closed desperately with him, both of them rolling into the mud.