This is the distinction between a mystery story and the more general category of crime fiction. The presence of the unknown is an important part of the appeal of the mystery. But it is always something deadly, lurking there in the dark. Something to be feared. Something to be conquered.
Mystery stories have a lot to gain from being translated into motion pictures.
But while much is gained in the transition from prose to film, much is also lost. When the onscreen detective attempts to explain his findings, his complicated deductions are often difficult to follow. And the medium of film may be TOO realistic to do justice to the theme of the unknown which is at the heart of mysteries. Comics, on the other hand, can be a sublime combination of the best of prose mysteries and cinematic noir. The scene of the crime can be illustrated in rigorous detail, and the reader is free to study it at length.