Glass Onion: Daniel Craig's Knives Out sequel continues Whodunit craze
question of what has prompted the recent resurgence in Whodunits is practically a Whodunit in itself. 
Is the US TV series Only Murders In The Building behind their sudden popularity? The Thursday Murder Club novels by Richard Osman? Kenneth Branagh's re-imagining of Hercule Poirot? Or do the continued sales of Agatha Christie novels show that Whodunits never left in the first place? 
g we can truly be sure of is it was not Colonel Mustard in the drawing room.
Whatever the cause, they are certainly big business at the moment. Netflix reportedly paid $450m (£376m) for the rights to two Knives Out sequels, the first of which, Glass Onion, is released on Friday.
riginal Knives Out movie starred Daniel Craig as detective Benoit Blanc, alongside Chris Evans, Jamie Lee Curtis and Ana de Armas in her breakout role. 
An old-fashioned yet innovative murder mystery, it was not the kind of landfill superhero movie or sci-fi blockbuster that has stormed the box office in recent years. And yet, that is exactly what it did - taking $313m (£255m).
Glass Onion, which stars an entirely new cast apart from Craig, is the first of what could be many sequels. Its writer and director, Rian Johnson, isn't surprised by the enduring popularity of Whodunits. 
"It makes sense to me, because it's the same thing that's always been appealing about the genre," he tells BBC News. "What's not to love? You have a rogue's gallery of interesting characters, you have a central charismatic detective, you have intrigue, you have mystery, comedy, human drama, all the ingredients are there.
"And for me, I'm a Whodunit junkie, I'm in heaven right now, the fact that there are more and more of these things, and that talents like Steve Martin are writing mysteries right now, to me, that's heaven."
Steve Martin project Johnson is referring to is Only Murders In The Building, which also stars Selena Gomez and Martin Short. The successful comedy-drama was recently renewed for a third season.
It follows three neighbours who become suspicious that a murder has been committed in their building. The trio of unlikely sleuths team up to host a true crime podcast and solve the mystery.
Another big-screen Whodunit released this year was See How They Run, starring Sam Rockwell and Saoirse Ronan in a standout comedic performance.
It flew somewhat under the radar because it was released in cinemas the day after the Queen died, but it's now available on Disney+.
"I think murder mysteries seem to wax and wane in cinema," the film's director Tom George tells BBC News. "But in the UK specifically, they're pretty constant. A year probably doesn't go by where there isn't some new imagining of an Agatha Christie story."
Set in London's West End in 1953, See How They Run follows a director's efforts to transfer the success of Agatha Christie's The Mousetrap from the West End to the big screen.
But everything goes wrong when a key member of the production team is murdered. It is a riot - a murder mystery within a murder mystery - and one of the season's most enjoyable films.
"I think the reason Whodunits keep audiences coming back to them as stories is the audience are trying to do the same thing that the detectives are trying to do - crack the case," suggests George.
"And that makes for a brilliant story. In any film you're trying to get the audience to connect with their lead character or characters as soon as possible by sort of putting them in their shoes. 
"So in a Whodunit, that's kind of baked in from the start. So from very early on, the audience are locked in with the detectives. They're watching each of the suspects and trying to figure out, what are their tells? What can I learn from this interaction? And it just makes for a really compelling story. 
"And there's something really reassuring about a puzzle where you know that all the pieces are eventually going to click into place - something you don't necessarily get in everyday life or true crime."
As well as being portrayed as a character in See How They Run, Christie was also an inspiration for Knives Out. Johnson says the queen of the Whodunit was a particular influence on him as a child. 
"It's a genre I just dearly love and have a real passion for," he says. "I thought about growing up watching the Agatha Christie adaptations with my family, and how they were some of my most treasured movie experiences.
"And I thought, I think there are people who are really going to want to see something like Knives Out. So we rolled the dice, but we really didn't know [it would be that successful]."
While worldwide book sales are always a nightmare to verify, Christie's own estate claims she is the best-selling novelist of all time, and is outsold only by the Bible and Shakespeare.
Last month, it was announced that Christie's The Mousetrap will finally open on Broadway, having played in London's West End for 70 years (Covid lockdowns excepted).
"The love of a Whodunit is embedded in British DNA, and I think we can trace much of this to Agatha Christie," says The Mousetrap's producer Adam Spiegel, who will also co-produce the show on Broadway.
"Her remarkable body of work both remains enormously popular with the public, and she is a source of great inspiration for the new generation of writers."
wo of Christie's most famous murder mysteries have been remade in recent years with Kenneth Branagh as Hercule Poirot - Murder on the Orient Express and Death on the Nile.
A stage adaptation of another Christie mystery, The Mirror Crack'd, is touring the UK, while two new TV series about the author fronted by Alan Carr and Lucy Worsley recently aired on Channel 4 and BBC Two respectively.
Whodunits are everywhere you look. The BBC's excellent reality series The Traitors saw 22 members of the public gathered in a Scottish castle, tasked with finding three traitors in their midst. It regularly topped the iPlayer chart.
Glass Onion's producer Ram Bergman suggests Knives Out has had a positive influence on the number of Whodunits being commissioned.
"People were afraid to make those," he says, "and I think because Knives Out was so successful, it kind of gave the freedom for the studios and streamers, 'there's an audience for these movies, let's make more of those'. Before, I think they were nervous about it."
gin with, Glass Onion feels somewhat disappointing after the brilliance of Knives Out. But once the set-up has been established, the film changes gear.
"Once the twists kick in, Glass Onion is edge-of-the-seat stuff," said the Evening Standard's Charlotte O'Sullivan. "The year's most ingeniously entertaining movie," is how Metro's Larushka Ivan-Zadeh described it.
But Kevin Maher of the Times said it is "a bad case of sequelitis", adding: "It's bigger, louder, emptier. The plot, which is the driving force of any murder mystery, is conspicuously flimsy, with very few surprises and little ingenuity."
So, how do you write a truly great Whodunit?
"First and foremost you come up with a story," says Johnson. "Who is the character we care about, what is their dilemma, and how are we going to have a satisfying ending? Not just in the Whodunit sense of 'oh that person did it', but a truly satisfying story.
"And you come up with that and then you have your spine, and you start layering things on, figuring things out, and planting things here and there. The mystery part is the fun part, the tough part is coming up with a movie that's going to keep people entertained for two hours."  