Read it through once

“There is but one thing to do. It must be done at once. You must put this piece of paper which you have shown us into the brass box which you have described. You must also put in a note to say that all the other papers were burned by your uncle, and that this is the only one which remains. You must assert that in such words as will carry conviction with them. Having done this, you must at once put the box out upon the sundial, as directed. Do you understand?”