Murders, detectives, cordoned-off crime scenes, and trench coats. These might be the first things that come to mind when you think of mystery movies, but they’re not essential ingredients. In fact, what exactly constitutes a mystery movie is, fittingly, a gray area.

Like the narratives it collects, mystery as a genre is malleable, multifaceted, and mutable to enough to describe films as disparate as Se7en and Picnic at Hanging Rock, the former a story about two cops hunting a serial killer who themes his murders around the seven deadly sins, and the latter, made in 1975, a dreamlike movie about schoolgirls going missing in Australia (and the kind of film Chloë Sevigny would definitely feature in if it were to be made now).

At its simplest, the mystery movie charts the solution of a problem or crime. There are two main types: the closed-mystery film, which conceals the identity of the perpetrator until late in the film, encouraging the audience to guess who it might be (Murder on the Orient Express), and the open-mystery film, which reveals the identity of the perpetrator at the beginning, such that the thrust of the film is about uncovering the intricacies of exactly how the crime took place (The Thomas Crown Affair). There are other mystery movies, however, which don’t fit neatly within those parameters: stories of a crime which is never solved, for example, or stories which aren’t about crimes, but are generally mysterious (Donnie Darko).

To prevent this all from becoming too much of a mindf*ck, we stripped our criteria right back when making this list of must-watch mysteries so that each that appears here is, well, a) mysterious in some way and b) not to be missed. From 1940s film noir to modern-day social thrillers, we’ve searched high and low to unearth some of cinema’s best kept secrets. Whether you’re looking for a classic “whodunnit” to unpick, or something more mind-bending to sink your teeth into, these are the best mystery movies of all time. Stay woke; there are some serious head-scratchers in here.