He watches Durdles for the purpose of finding how the drug which he has administered works, with a view to future operations on Edwin. Durdles is now in such a state that “he deems the ground so far below on a level with the tower, and would as lief walk off the tower into the air as not.” All this is apparently meant to suggest that Jasper, on Christmas Eve, will repeat his expedition, _with Edwin_, whom he will have drugged, and that he will allow Edwin to “walk off the tower into the air.” There are later suggestions to the same effect, as we shall see, but they are deliberately misleading. There are also strong suggestions to the very opposite effect: it is broadly indicated that Jasper is to strangle Edwin with a thick black-silk scarf, which he has just taken to wearing for the good of his throat. The pair return to the crypt, Durdles falls asleep, dreams that Jasper leaves him, “and that something touches him and something falls from his hand. Then something clinks and gropes about,” and the lines of moonlight shift their direction, as Durdles finds that they have really done when he wakens, with Jasper beside him, while the Cathedral clock strikes two. They have had many hours, not less than five, for their expedition. The key of the crypt lies beside Durdles on the ground. They go out, and as Deputy begins stone-throwing, Jasper half strangles him. PURPOSE OF THE EXPEDITION Jasper has had ample time to take models in wax of all Durdles’s keys. But he could have done that in a few minutes, while Durdles slept, if he had wax with him, without leaving the crypt. He has also had time to convey several wheelbarrowfuls of quicklime from Durdles’s yard to Mrs. Sapsea’s sepulchre, of which monument he probably took the key from Durdles, and tried its identity by clinking. But even in a Cathedral town, even after midnight, several successive expeditions of a lay precentor with a wheelbarrow full of quicklime would have been apt to attract the comment of some belated physician, some cleric coming from a sick bed, or some local roysterers. Therefore it is that Dickens insists on the “utterly deserted” character of the area, and shows us that Jasper has made sure of that essential fact by observations from the tower top. Still, his was a perilous expedition, with his wheelbarrow! We should probably learn later, that Jasper was detected by the wakeful Deputy, who loathed him. Moreover, next morning Durdles was apt to notice that some of his quicklime had been removed. As far as is shown, Durdles noticed nothing of that kind, though he does observe peculiarities in Jasper’s behaviour.