Basics of the Mystery Story

In this post, I will go over the basics of a mystery story, over the pieces you need to have in order to have a successful story of that kind. I’m not going into specific directions, such as the ‘Locked Room Mystery’ (not this time, that is), and I will use a specific book to present them - “Evil under the Sun” by Agatha Christie.

“Evil under the Sun” is not the most well-know novel by Agatha Christie, not even the most well-known Hercule Poirot story, but it’s one of my favourites, because it plays extremely well with two aspects of a crime: time of death and identity of the body (also the identity of other people).

The novel starts, as all Agatha Christie stories, with establishing the setting. The past of the hotel where the murder will happen is explained, Hercule Poirot is introduced and the basics are laid out. The people staying at the hotel are introduced, so we have a good picture of who might be behind the murder. The victim is introduced early and it’s suggested from the beginning that Arlena Marshall (Arlena Stuart while she was still on stage) had it coming - that she made more than enough enemies in her life. That is one of the first things to keep in mind about a mystery story. A murder where only one person is a suspect is not a mystery. It’s an open-and-shut case. If there’s not a number of possible suspects, then there will not be a mystery at all. Arlena Marshall is a good victim, because of her character and because of her past. She has broken hearts, cheated on people, talked people down. She is only looking out for her own pleasures, not caring whether or not she hurts people in doing so. Even at a little seaside hotel, the list of possible murderers is, therefore, long - which is how it should be.

The murder doesn’t happen right at the beginning, either - that is not Agatha Christie’s style. She introduces the situation very well and gives the reader a chance to get to know the various characters who will later on play a role. But that is her style, it’s not a necessity for a mystery story as a such. Many stories do well with starting right with the murder and establishing the setting later on. By the time Arlena winds up strangled, we are well-acquainted with everything and everyone and can easily follow Hercule Poirot on his quest for the truth.

At the beginning, we have the following parts of the mystery: the setting, the detective, the victim, the array of suspects with their motives. Then the murder happens. Arlena Marshall leaves the hotel earlier than usual to take a float to one of the small coves of the island the hotel is on (not one which has sun in the morning, either, so it’s clearly not for sunbathing). Hours later, Mr. Redfern (who is less of a suspect than his wife, since he has a little affair with Arlena) finds Arlena together with another guest, Miss Brewster (who has not motive at all) - he’s in the green there, obviously, having been in plain sight of Poirot and a host of other guests all morning so far. He sends the Miss Brewster back to the hotel, knowing she won’t climb up the ladder of the cove, because she’s afraid of heights, but take the boat instead. By the time Poirot arrives, there is no doubt Arlena Marshall is dead - strangled by someone with strong hands, which takes Mrs. Redfern out of the list, for she has exceptionally small hands and a fear of heights herself (so she couldn’t have used said ladder either). Still, there’s enough people on the island who would like to see Arlena dead.

It’s also established early that a stranger is out as the murderer - the island is hard to reach during high tide, so nobody can just have walked over, killed her, and disappeared. The murderer therefore must be someone who spent the morning on the island. This is another important part - establish that there is only a limited pool of suspects and it can’t have been a chance death. Because the reader wants to investigate alongside the detective and thus the mystery must be solvable - a chance killer won’t be found during an investigation and luck shouldn’t play a role for the solution.

Next, Poirot needs to establish the basics of the crime. He himself helped Arlena Marshall to push her float into the water that morning, so he knows she was still alive around quarter past ten. When Miss Brewster and Mr. Redfern reached the cove, it was about quarter to twelve, which means that by that time, Arlena was dead. The first question then is who has no alibi for the hour (it takes about half an hour to reach the cove  from the beach with a boat or float) between Arlena’s arrival in the cove and the time she was found. Nobody, it turns out. Even people who thought they had none were seen or heard by someone and thus given an alibi they didn’t even know they had. Another important part of the mystery is established - there’s something about the established facts which is wrong. Otherwise, it wouldn’t be a mystery, it would merely be a case which needs a little longer to be closed.

Because of that, Poirot has to take a step back and look at the facts again. He knows that Arlena Marshall is dead and he knows that she was strangled. That much he has seen with his own eyes, so he can take it for face value. A survey of the cove shows him that there is a small cave around in which a quantity of heroin has been hidden. It takes another realisation to turn Poirot’s mind to the truth: the only person who was close enough to identify Arlena when she was found by Mr. Redfern and Miss Brewster was Mr. Redfern. Miss Brewster didn’t go too close to the body and she went back with the boat - afraid of staying with a dead woman when the murderer might still be close by. What Miss Brewster did see was a body with Arlena’s white bathing suit, jade-green Chinese hat, and bronzed limbs sticking out. As Poirot pointed out himself at the beginning of the book, those bronzed bodies at the beach all look the same, so was it really Arlena? And was she dead or alive at that point? Because if it wasn’t Arlena or she wasn’t dead, Redfern is no longer beyond suspicion.

There are other strange things which turn up during the investigation, such as a bottle being thrown out of a window and a bath nobody admits to have taken. Slowly, things come together and, finally, Poirot is able to solve the case. That is an important part - the detective and through them the reader will have to look at things from a different perspective. The case needs a twist, otherwise the mystery isn’t good enough. I will not disclose the twist here, in case you want to read the novel yourself.

Let’s review the parts to keep in mind.

Establish a victim with a host of enemies. There needs to be a host of suspects after the actual deed is done.

Make sure the number of suspects is not too high, though, and they are all introduced. You don’t want the victim to be a chance victim or a professional killer in the story, because in both cases, your detective will not be able to solve the case. At the same time, you don’t want the reader to be confused by the pure number of possible murderers.

Let the detective establish the basics of the crime and start their investigation. You need to give the reader something to work with, so let the detective detect. Certain facts, such as the identity of the victim and the way they were murdered, are usually easy to detect. Time of death often can be found out early, too.

Have a twist. Something about the case just won’t come together, all suspects have alibis, there’s no way of saying who did it.

Make the detective take a step back and choose a new direction. Through examining the facts again, the detective should finally be able to find the right lead and the culprit.

You can play the last two stages several times, but stop it before it gets too obvious. Two false ‘right’ leads should be enough. Just as ten suspects or less should be enough. If you have too many, the reader will not be able to keep them all in mind.

Around those basics, you can spin whatever case you want. The mystery will always work out, no matter the genre. Keep in mind that a mystery story is always a story about a puzzle, a puzzle which the reader will solve alongside the detective. The reader needs to be able to do so, so give them all the information as the detective gets it.