For the inscrutable yet precocious personalities of Miles and Flora evident in the 1961 film 'The Innocents'. As well, the ghosts of that movie are fleshed out nicely in this prequel. Quint is a morally repugnant character, sadistic and controlling, but he's also darkly magnetic as the corrupter of the lovely young governess who submits to (and even embraces) his perverted ideas of sexuality. Together they are fated to become the imprisoned souls that haunt the estate. Together they have inflicted unknowable damage to the psyches of the children.
Brando is very good in the role of Quint. He gives the character a credibility and powerfulness that one would expect from a personality who will ultimately refuse to leave, even after his bizarre death. Few actors would be convincing enough to portray such a reprehensible protagonist and still be vaguely, mysteriously likable. That Brando can deliver this affect with legitimacy is not surprising, genius that he is. Another who might have been very interesting to watch in this role is Dirk Bogarde.
The director's visual styling of the film is it's most unfavorable aspect and prevents it from being excellent. In any case, this unusual little entry has always been a tad underrated. I suspect that now that Marlon has passed on an overdue re-assessment is likely.