Opening with notes audibly resembling a heartbeat monitor, before swaying into a diegetic sonata, this year’s Swiss Oscar entry “My Little Sister,” chillingly captures the frightening feeling of sitting beside a loved one in unspeakable pain, knowing there’s not a thing you or the medical staff can do about it. “Your mask,” a bed-side nurse reminds formerly renowned playwright, Lisa (Nina Hoss) after dozing off next to her twin brother, Sven (Lars Eidinger), an acclaimed actor in the Berlin theater scene, whose leukemia has become bellicose again.