A sudden, inexplicable death at a wedding celebration triggers a series of supernatural events that threaten the legitimacy of a noble lineage. Manfred, the Lord of Otranto, attempts to secure his family's future through a desperate marriage, but he is thwarted by ancestral curses, spectral manifestations, and the sudden appearance of a giant helmet. The narrative follows a linear progression, focusing on the frantic efforts of the characters to navigate the shifting alliances and terrifying occurrences within the castle walls.

Readers and critics frequently identify this work as the foundational text of the Gothic genre, noting its influence on subsequent horror literature. Discussion often centers on the deliberate use of melodrama and the stark contrast between the rational and the irrational. Many observers highlight the author's intentional departure from the realism prevalent in his time to favor suspense and architectural dread. The work is often studied for its structural simplicity and its role in establishing tropes that remain common in modern gothic fiction today.