After a perversely fascinating start, a darkly comic psychodrama goes plain psycho in “Bad Family,” from Finnish writer-helmer Aleksi Salmenpera (“Producing Adults”). At first, this tale of an overprotective dad who believes his teen son is shtupping a long-lost sister builds a transgressive tension redolent of guilty pleasures such as “The Stepfather” or Salmenpera’s own “Man’s Job.” But the pic loses its way at the midpoint, becoming a tonal roller-coaster that skitters to a stop. The pedigree of Salmenpera and producer Aki Kaurismaki could leverage further fest play, though the pic is likely to do best in ancillary.
Mikael (Ville Virtanen, so tightly wound it’s scary) micromanages his good-looking high school son Dani (Lauri Tilkanen) until the day daughter Tilda (Berlin fest shooting star Pihla Viitala) appears. Soon, youthful rebellion fills the air and an obsessive father’s mind recoils at thoughts of incest until madness sets in. In the beginning, serious thesping by the three principals suggests psychological depth, but the script eventually leaves them high and dry. Lenser Tuomo Hutri gives the proceedings a hyperrealist look, while a lightly used keyboard-and-percussion score adds mocking commentary.