The 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 release of 2019's box office smash Knives Out? 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?
The only thing 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.
The original 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."
The 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."