Almost every great detective has a great sidekick. Leading the pack, of course, is Sir Arthur Conan Doyle with his team of Sherlock and Watson.
In the Sherlock Holmes mysteries, Dr. John Watson is Sherlock's sidekick and the narrator.
The character created by Doyle to support Holmes is modest and intelligent—but not as smart as Holmes. A former military doctor wounded in India, Watson is far from dull. Still, like most readers, he doesn't share Holmes's detecting capabilities, powers of observation, and lightning-swift reasoning, which is a blessing for readers, for it's Watson who explains and shows the readers Holmes's admirable characteristics through his narrative and descriptions.
Another of the best-loved investigating pairs are Rex Stout's Nero Wolfe and Archie Goodwin. Wolfe is a New York City private investigator. His sidekick, Archie Goodwin, does the lion's share of investigating because Wolfe doesn't like to leave the brownstone, but it's Wolfe who provides the keen intellect. Archie's role is to bring wit and a fast-paced narrative to the reader. Rex Stout has published around 80 novels and novellas detailing their various cases. Wolfe and Archie are right up there with Dr. Watson and Sherlock.
Contemporary author Faye Kellerman created the Peter Decker and Rina Lazarus team. Decker is a Los Angeles cop investigating crimes in a conservative Jewish community. His supporting character is Rina Lazarus, with whom he falls in love. He converts to Judaism for her, and they are married. Together they become involved in several mysteries in Jewish communities. Although she isn't a police detective, she is vital to the investigations for her deep understanding of Jewish culture and faith.
A little outside this norm is Agatha Christie's Miss Marple, who seems to work alone. She is an independent woman of independent means. Elderly, and unassuming Miss Marple uses her advanced years and knitting needles to stay out of the limelight which allows her to observe without being noticed. She is a student of human nature and able to solve complex crimes not only because of her shrewd intelligence but because over her life living in St. Mary Mead, she has had the benefit of infinite examples of the nastier side of human nature.
Her friends and acquaintances function in the role of supporting characters, and they are sometimes bored by her frequent analogies. Still, these analogies often lead Miss Marple to a more profound realization about the true nature of the crime. It isn't until her later years that her companion, Cherry Baker, moves in and makes her first appearance as the sidekick in The Mirror Crack'd from Side to Side.
Perhaps one of the most unique and unexpected characters in a supporting role is M. Hercule Flambeau, a reformed criminal in the Father Brown series by G. K. Chesterton. Flambeau is always amazed at how a priest could have such a depth of understanding and insight into the criminal mind. The good priest explains that while he must protect the sanctity of confessions and not give specifics, people reveal their sins and show the evil in the human heart.
In the first chapter of The Secret of Father Brown, the priest tries to explain that he doesn't look at criminals scientifically from the outside.
"I am inside a man. I am always inside a man, moving his arms and legs; but I wait till I know I am inside a murderer, thinking his thoughts, wrestling with his passions; thill I have bent myself into the posture of his hunched and peering hatred; till I see the world with his bloodshot and squinting eyes, looking between the blinkers of his half-witted concentration; looking up the short and sharp perspective as a straight road to a pool of blood. Till I am really a murderer."
Flambeau was a skilled and highly successful thief with an intellect equal to Father Brown's. In The Secret of Flambeau, he reveals, "Have I not heard the sermons of the righteous?... Do you think all that ever did anything but make me laugh? Only my friend told me that he knew exactly why I stole, and I have never stolen since."
There are as many famous sidekicks as there are famous detectives, including Captain Hastings, in the Hercule Poirot books by Agatha Christie and Brother Eadulf in Peter Tremayne's Sister Fidelma series. In Dashiell Hammet's The Thin Man, Nora Charles is a glamourous sidekick to her husband, Nick. But why do authors create these characters?
Like the supporting stage and film actors, the mystery book sidekicks have a vitally important role, both to the principal characters and to the readers or audience.
A good sidekick is usually the polar opposite of the detective. Watson is kind, patient and loyal, and in many ways ordinary. The opposite of Holmes.
Like Watson, Captain Hastings, Hercule Poirot's supporting character is also ordinary, loyal, and determined but lacks Watson's military experience.
The sidekicks showcase the detectives' intelligence but cushion the readers from feelings of inferiority. The sidekick usually seems to be a rather ordinary person, with exceptions, like Flambeau, who is anything but ordinary.
For the sake of storytelling, good detectives have quirks and personality flaws. They allow the sidekick to show opposite and balancing characteristics, provide an avenue for readers to understand what the main character is thinking, ask the readers' questions, explain the detective's reasoning and methods and any cryptic or scientific terms. Sometimes, the sidekick inspires the detective to look at a situation in a new way, which wouldn't be evident without the secondary character's input. This can provide a stalled plot with an escape valve. Most important, however, the sidekick can never be interchangeable with the main character.
From the outset, Nora Charles is a Nob Hill socialite. Nick Charles is a retired detective who has been exposed to the seedier sides of life. This seemingly incompatible couple marry and combine wits to solve crimes.
In my Housekeeper Mystery Series, Mrs. B. is the leading amateur woman detective. She's impulsive, willful, nosy, outspoken, likes people, loves to cook, and loves cats.
Father Melvyn Kronkey is her boss and pastor of St. Francis de Sales, Roman Catholic Church. He is a good man and a devout priest who will serve as an anchor for the curious and impulsive Mrs. B.
An essential part of a mystery writer's tool kit, the sidekick provides color, contrast, relief, and assistance to the reader. They often help the main characters grow, evolve, and sometimes change course altogether.