As the last step in the scheme, Gratus summarily removed the old keeper of the prisons; not because he knew what had been done-for he did not-but because,knowing the underground floors as he did, it would be next to impossible to keep the transaction from him.Then, with masterly ingenuity, the procurator had new maps drawn for delivery to a new keeper, with the omission, as we have seen, of cell VI. The instructions given the latter, taken with the omission on the map,accomplished the design-the cell and its unhappy tenants were all alike lost.