Participants in The Purge were getting younger each year.
There are mystery yarns, and there are mystery yarns. From complex, baffling ones with well thought-out resolutions, to obviously contrived ones with “big reveals” you can figure out well in advance of the (usually clueless) characters.
Then there are mystery yarns that start out as such, and turn into something quite different altogether. The Outsider, an adaptation of the 2018 Stephen King novel, is one of these.
Summary:
Whodunnit, howdunnit, or whatdunnit?