The four sentences (labelled $1, 2, 3$ and $4$) given below, when properly sequenced, would yield a coherent paragraph. Decide on the proper sequencing of the order of the sentences and key in the sequence of the four numbers as your answer.
- What precisely are the "unusual elements" that make a particular case so attractive to a certain kind of audience?
- It might be a particularly savage or unfathomable level of depravity, very often it has something to do with the precise amount of mystery involved.
- Unsolved, and perhaps unsolvable cases offer something that "ordinary" murder doesn't.
- Why are some crimes destined for perpetual re-examination and others locked into permanent obscurity?