I’ll be discreet. “3 Faces” may be modest and low-key on the surface, but its surprises are worth preserving, its insights casually profound. At the heart of the story is a mystery: What happened to Marziyeh (Marziyeh Rezaei), a teenage girl and aspiring actress from Iran’s Turkish-speaking Azerbaijan region, who has suddenly gone missing? Before she vanished, Marziyeh, whose family strongly disapproves of her choice of calling, sent an alarming self-shot video to the famed actress Behnaz Jafari (playing herself). Jafahi was sufficiently rattled by the footage that she has now come to the girl’s village in search of answers, chauffeured by none other than Panahi himself.