A town where everyone knows everyone and nothing is what it seems.
Why it is hard sci-fi
Soft. Lynchs 1990 series engages with science fiction only intermittently, primarily through the Black Lodge and the White Lodge. What earns it a place is the consistency of the procedural texture. An FBI investigation, a small-town economic ecology, and a recurring set of dream-state interrogations with a working internal grammar. The shows return season in 2017 commits to a literal nuclear-test origin for its evil, which is the closest it gets to a science claim.
Science inside it
A 1945 nuclear-test origin event for the shows central evil, a working dream-state interrogation that uses real free-association methods, and a small-town federal investigation procedure. The shows interest in radio frequencies as a carrier for non-human consciousness is its second-most explicit science claim.