Most murder cases can be divided roughly into two categories; murder by poison, and murder by violence. In the former method, it seemed that the murderer hoped that the cause of death would be certified as from some other cause, or that if the poison be traced, that it will not be proved that he or she administered it. The other type of murder sets a very different problem. It is this... Either the murderer must disappear, or the body must disappear - or both.