When the police investigate a murder, they generally look into the victim's life to find out who might have had a motive for the killing. They look for physical evidence, too, of course. That job is made even harder when there's more than one killing. Then, the police have to not only look into each victim's life, but also find whatever link there is between the victims. It's those links that often provide the police with valuable clues to the murderer. In crime fiction, those links can be tricky. They need to be obvious enough that it's reasonable that the sleuth would find them. At the same time, though, they need to be subtle enough that the story isn't spoiled as soon as the second death occurs.
Sometimes, there seems to be a link on the surface, but it leads, as you might say, in the wrong direction. That's what happens in Agatha Christie's The ABC Murders. In that novel, Hercule Poirot receives a cryptic note telling him there's going to be a crime in Andover on a certain date. At first, it's considered a meaningless prank, or the work of someone who's "not all there." Then, tragically, Alice Ascher is killed behind the counter of her newsagent shop. On the countertop is an open ABC railway guide. The police look into Alice Ascher's life, but the only real suspect, her estranged husband, seems to have an alibi, and wasn't seen near the shop on the day of the murder. Then, Poirot receives another note. Sure enough, another body is discovered, also with an ABC guide nearby. Then a third body is found. It seems that the only things linking these bodies are the railway guides and the notes to Poirot. The victims didn't know each other and have little in common. So the killings are put down to the work of a serial killer. In fact, the police think they have their man when another link among the victims is found. But, in true Christie style, that's not the "real" link among the victims. When Poirot does discover the link, and the real reason for the murders, he's able to find the killer.
In Three Act Tragedy (AKA Murder in Three Acts), Poirot is invited to a cocktail party and dinner at the home of Sir Charles Cartwright, a famous actor. While everyone's enjoying cocktails, one of the guests, Stephen Babbington, is poisoned. At first, no-one can really believe he was poisoned. He didn't have a fortune to leave, and didn't seem to have any enemies; in fact, he was a beloved clergyman. Not only that, but there doesn't seem to have been an opportunity for anyone to poison him. Poirot himself isn't even sure it's a murder at first. Then, another death occurs; Dr. Bartholomew Strange, a Harley Street specialist, dies in his country home in Yorkshire in the same way. Some of the guests who were present at Sir Charles' party are also present at Sir Bartholomew's party, so the first assumption is that Sir Charles may have found out information about Stephen Babbington's death, and wanted to confront the culprit. That doesn't turn out to be the link between the deaths, though; instead, the link is in the killer's personality and experience.
In Dorothy Sayers' Whose Body?, Lord Peter Wimsey discovers the link between an unidentified body found in a bathtub, and a missing well-known financier. Interestingly enough, it's not the obvious connection you might think it is. Alfred Thipps is an architect for the Dowager Duchess of Denver, Wimsey's mother. One day, he finds the body of a man in his bathtub. Immediately, the police suspect him of the crime, but the Duchess is sure that he's innocent, and asks her son to help. In the meantime, Sir Reuben Levy, a famous financier, seems to have disappeared at the same time as there's been some strange stock market activity. Although the body in the bathtub is not that of Sir Reuben, Wimsey comes to believe that the events are linked and, as things turn out, they are. The link among them turns out to be, in an odd way, location. Once Lord Peter figures out where the "hub" is of the action of the story, he's able to find the link between the bodies, and the explanation for Sir Reuben's disappearance, as well as the appearance of the body in the bathtub.
In Caroline Graham's A Ghost in the Machine, we meet Dennis Brinkley, a financial consultant, who is appointed executor of wealthy Carrie Lawson's will. When she dies, much of her fortune - and her home - goes to her nephew Mallory Lawson and his family, providing they hire her companion, Benny Frayle. The Lawsons have no objection, and all seems well at first. Then one day, Benny discovers Dennis' body beneath one of the antique torture devices he is fond of collecting. Benny believes that Dennis' death was murder, but she can't get anyone - including Inspector Barnaby - to believe her at first. Then, there's another death. Psychic Ava Garrett is poisoned one night. At first, the only link between the two deaths seems to be Benny Frayle, who was friends with Dennis Brinkley and had gone to see Ava Garrett. In fact, Benny is accused of both crimes. As it turns out, though, there's another link between Dennis Brinkley and Ava Garrett. When Inspector Barnaby starts to look into both deaths more closely, he finds a hidden financial connection that leads him and Sergeant Troy to the real murderer.
There's an ingenious link between a robbery and a murder in Colin Dexter's The Jewel That Was Ours. Laura Stratton and her husband, Ed, are traveling with a group of other American tourists on a trip through historic English cities. One of the stops on their tour is to be Oxford. While they're there, Laura intends to donate a valuable relic she owns - the Wolvercote Tongue, part of an Anglo-Saxon belt buckle - to the Ashmolean Museum, which owns the rest of the buckle. On the afternoon of their arrival, Laura suddenly dies and the Wolvercote Tongue disappears. Inspector Morse and Sergeant Lewis are put on the case, and at first, treat it like a theft. Then, the next day, Dr. Theodore Kemp, curator of the Ashmolean, is found murdered. Morse thinks the two cases are related, and he and Lewis begin to investigate them that way. The only trouble is, the obvious connection between the two events doesn't seem to pan out. None of the suspects seems to have been able to both steal the Wolvercote Tongue and kill Kemp. In the end, and after some "wrong turns," Morse finds out what the real connection is between the missing belt buckle and Kemp's death. It turns out to be a very unexpected connection having as much to do with serendipity as with anything else.
There's a fascinating hidden connection among the deaths of Bethany Friend, George Saffell and Stuart Wagg in Martin Edwards' The Serpent Pool. Six years ago, Bethany Friend's drowned body was found in the Lake District's Serpent Pool. There wasn't convincing evidence of murder, and the case was never solved. Now, six years later, first book collector George Saffell, and then attorney Stuart Wagg are also found dead. At first, there doesn't seem to be a common motive for their murders. Nor does it seem that they had a common enemy. But DCI Hannah Scarlett thinks the three deaths are related. Fern Larter, Hannah's best friend at the Cumbria Constabulary, is willing to get any help she can on the Saffell and Wagg cases, which she's investigating, so Scarlett shares what she's learning about Bethany Friend's death with Larter. As Scarlett gets closer to the truth about the three cases, she realizes that the link among them has to do with a network of relationships - and an obsession. She also realizes that she's going to have to catch the killer before there's another death much closer to home for Scarlett.
Sometimes, those links between two or more deaths are obvious, such as when a killer silences a person who's witnessed a crime. But it can be just as intriguing - maybe even more so - when the link is not so obvious. Then, the sleuth has to put together the disparate pieces of the puzzle. So long as the link is not too contrived, it can be an effective way to keep sleuths guessing and readers turning pages. What do you think? Do you think those "hidden links" are too unrealistic?