Complex sentence: Once, during a raid by the Cowichan, the women and children vanished without a trace and, since then, the Plateau has become taboo for it was believed that it was inhabited by evil spirits who had consumed those they had sent.
Split into simpler sentences: Once, during a raid by the Cowichan, the women and children vanished without a trace. Since then, the Plateau has become taboo for it was believed that it was inhabited by evil spirits who had consumed those they had sent.