midnight
`` The first aim of the writer is to show , from the brevity of the interval between Marie 's disappearance and the finding of the floating corpse , that this corpse can not be that of Marie . The reduction of this interval to its smallest possible dimension , becomes thus , at once , an object with the reasoner . In the rash pursuit of this object , he rushes into mere assumption at the outset . ` It is folly to suppose , ' he says , ` that the murder , if murder was committed on her body , could have been consummated soon enough to have enabled her murderers to throw the body into the river before midnight . ' We demand at once , and very naturally , why ? Why is it folly to suppose that the murder was committed _ within five minutes _ after the girl 's quitting her mother 's house ? Why is it folly to suppose that the murder was committed at any given period of the day ?