In broad strokes, there are only a few reasons to murder someone:

1. Gaining money or other forms of power
2. To pave the way for love
3. Revenge
4. To gain status that properly belongs to the victim
5. To protect one’s status

These correspond, roughly, to the deadly sins:

1. Greed
2. Lust
3. Wrath
4. Envy
5. Vanity

Today I want to consider murder for revenge. It further subdivides into two possible situations:

1. The murderer is fine with being destroyed in the process
2. The murderer wishes to suffer no repercussions

The former can make an interesting story (such as the sub-plot in Chesterton’s The Sins of Prince Saradine), but it’s not easy for it to sustain a mystery. The main problem is that the murderer should, by hypothesis, confess. This can, however, be handled.

The first way to handle this is to have the murderer leave. This is hard to work unless he thinks the crime won’t be discovered and so no explanation is necessary. That can be done, though, especially for historical crimes being discovered and investigated only years later.

The second way to handle this is to have the murderer leave a confession before leaving but to have the confession intercepted by someone who wants to use the occasion to murder someone by framing him for murder. This is a very workable sort of plot, though it will be complicated.

The third major way is to kill the murderer before he can confess. This may be the most interesting option, especially if he is killed by the victim. Of course, if the murderer is murdered by his victim, this will not be mysterious unless at least one of them uses a scheme for which he does not need to be present, which is where the interesting part comes from. It is very hard to suspect a dead man of murder. If there is anyone one will leave off suspecting of a crime, it’s a dead man.

In a Cadfael story (Saint Peter’s Fair) Hugh Beringar remarks that babes and drunks are the world’s only innocents. But this is not an exhaustive list. Who is so incapable of harm as a man already dead?

What’s specially interesting about two people who have murdered each other is that with any conniving at all, the author can contrive to have everyone suspect them of being murdered by the same person, and this will be a very strange person indeed to have two enemies with so little in common. It also means that the murder will seem to have been done very craftily when it was in fact done very simply. Or at least one of them will be like that. There are absolutely wonderful possibilities for misdirection, here.

(I really want to write a story like this some day. I probably should first write a story with at least two victims at the start who were killed by the same person, so it’s not obvious, though.)

The other major option, and which is more common because it can far more easily sustain a mystery, is for the one seeking revenge to wish to avoid repercussions for his crime. This provides a simple reason for why he does not confess. It can sustain a mystery with little difficulty at all.

It can, of course, be made far more complex than the simple case. The variation that I suspect is most interesting, or at least that I personally find most interesting, is of introducing the complication of the passage of time. This can either be put between the original offense and the present, or between both the original offense and the revenge, and the present.

Of the two, my favorite is probably the ones where the revenge is recent but the offense in the past. This is probably most classically done with the child who grows up to avenge a parent, but this possibly should be avoided because it is common enough that, these days, the average reader might count the years since the crime in the past and guess the killer simply based on his age.

It comes to mind that an interesting way around that problem might be to give the murderer some scruple in his revenge, such as waiting for the 18th birthday of the vicitm’s youngest child, on the theory that his children should not be punished for the crime of their father. Something like that would throw a wrench into figuring out the culprit by simple calculations, at least.

There are more variations on murder for revenge, but this post is getting long enough that I think I’ll leave them for later. Enjoy writing your murder mysteries about revenge, and God bless you.