Final answer:
Without additional context, it is not possible to determine the cause of death for Robert's wife Beulah from the given information. The inquiry seems rooted in literary context, suggesting a tragic or symbolic death, but further details are needed. The cause of death is generally depicted as being linked to themes of imperfection, obsession, and Gothic illness.
Step-by-step explanation:
The question does not specify which Robert's wife named Beulah you are referring to, as there are multiple literary and historical figures named Robert with wives named Beulah. Without more context, it's not possible to provide an accurate cause of death for Beulah. However, in the text references provided, it's implied that Beulah died due to a tragic event or circumstance linked to her husband's actions or situation. For instance, the extract mentioning that as the birthmark faded from her cheek, symbolizes the loss of life due to the obsession with perfection. Another context describes the Gothic overtones of illness and death in an ancestor's family. Nevertheless, to answer your specific query about Robert's wife Beulah, more information is needed to conclusively determine the cause of her death.