A Souls and Shells Scenario for the Curse of Strahd
From the introduction:
There is a married couple who both have souls, and they want to have a child, but the mother keeps losing the baby. They decide, in their anguish, that the right soul isn't yet available. Their solution finds them often socializing with people at the taverns, "interviewing" unsuspecting candidates for their future child's soul. The ones who pass their test are invited to their place, where they are murdered, in the hopes that they can make that soul available for their future child.