Most good stories start with a fundamental list of ingredients: the initial situation, conflict, complication, climax, suspense, denouement, and conclusion. Great writers sometimes shake up the recipe and add some spice.
Exposition (Initial Situation)
At the very beginning of the book, ten strangers are on their way to a fantastic place called Soldier Island, which doesn’t sound quite as nice as, say, Baja, but hey! Islands are cool.
They’re understandably excited since the place is supposedly owned by an eccentric party boy millionaire—think Leonardo Dicaprio in any of his post-2000 movies—and they think they’re in for a fun holiday. But when they get there, the host is nowhere to be found and they find themselves amongst an eclectic mix of strangers. No worries, though! There’s always dinner and drinks to be had.
Rising Action
Things start to get a little dicey when a loud, booming voice comes out of nowhere and accuses each of them of committing a murder. Talk about a complication.
Everyone is pretty freaked out, natch, especially when they realize that the voice is coming from a prerecorded gramophone record. But it’s about to get a lot creepier. Soon afterwards, Anthony Marston takes a drink and falls down dead. And the next morning, Mrs. Rogers doesn’t wake up on time—or at all. Something very peculiar (and dangerous) is afoot on Soldier Island…
Climax
One death is weird, two is suspicious, but three? Now we’re talking serial killer. And when General Macarthur is bludgeoned to death from behind, just like the creepy nursery rhyme predicts, it’s clear that someone is very cleverly killing the guests off one by one. So who is it? After a thorough—and fruitless—search of the island, the remaining guests conclude that …. one of them is the killer. Aiiiiiiiiiiiiii!
Falling Action
As the novel toodles along toward its conclusion, people just keep dying. Mrs. Brent is “stung” by a hypodermic needle, Justice Wargrave is shot while wearing a judge’s robes, Dr. Armstrong drowns in the ocean, Blore is “hugged” by a bear (or rather hit with a bear-shaped clock), Lombard is shot by Vera, and Vera hangs herself just like the last little soldier boy does in the poem.
At the ends of this section, we’ve got ten dead bodies and no clue as to who actually killed them all. What a pickle! Someone better call in a consulting detective.
Resolution (Denouement)
Luckily, and no thanks to the police, we get an epilogue to clear everything up. After a bunch of more fruitless investigation, a literal message in a bottle washes ashore. And guess who the killer is? None other than man of law Justice Wargrave, who takes his commitment to justice a little too seriously—so seriously that he wants to make everyone pay for the unconvictable crimes they’ve committed by… wait for it… engineering the perfect, unsolvable mystery, even pretending to kill himself so he’d appear to be one of the victims.
The problem with the perfect, unsolvable mystery is that it leaves you without all the glory of having orchestrated the perfect, unsolvable mystery. But Wargrave still suffers from some serious egotism, so he wrote a letter and tossed it out to sea so he could be recognized for his cleverness. (And total psychopathy, but that probably wasn’t his goal.)