After the death of her children, Anna partakes in a dab of opium to ease her pain. It works like a charm: instead of obsessing all day about the things that she's lost, she's able to enjoy a thoughtless bliss. Needless to say, however, none of this ends well.

Anna relieves a great deal of her suffering by taking opium, but the feeling is only temporary. Even worse than that—her supply is limited. In this way, Anna's drug use ends up biting her in the butt because it only highlights the emotional pain she's been fighting against since the plague arrived in Eyam.

This might explain why Mompellion is so different from the stereotype of a Puritan minister. Before his life as a professional man of god, Mompellion was your average working-class Joe, which gives him a uniquely egalitarian perspective on society.