Under Capricorn (1949) - best one-shot (actually two-shots) sequence.

My favorite sequence from the film (a 1m40s take combined with a 5m20s take); elaborately staged to move in and out of the house and back and forth through multiple rooms, while the new guest (Wilding) pieces together the subtext being revealed, all of it leading up the dramatic introduction of the mistress of the house for the first time in the film.