Final answer:
After Madeline dies, Usher plans to preserve her corpse for a fortnight before its final interment in a vault within the main walls of the building.
Step-by-step explanation:
After Madeline dies, Usher plans to preserve her corpse for a fortnight before its final interment.
This is done due to the unusual character of Madeline's malady and the remote and exposed location of the burial-ground of the family. Usher's intention is to temporarily entomb Madeline in a vault within the main walls of the building.