The plot begins in a London tavern with Edgar Allan Poe telling a story and claiming his works are based on actual events. A persistent journalist insists that only the living are to be feared. Another man at the table offers a dare that the journalist won't be able to spend a night in his haunted castle. He says, "All those who accepted my wager died in the castle." The journalist accepts. The Lord of the castle, Poe and the journalist make the 2-hour carriage ride to the castle, where the journalist refuses a last chance to back out, and the carriage drives off. The journalist makes his solitary way through the creaking iron gate, through the dark eerie cemetery up the winding path and stairs until he is finally inside. All that was creepy enough, and the horror hasn't even begun.
1000 Misspent Hours has a mixed review, praising a "stark, monochrome moodiness" and "a great set, a sound premise, some very solid acting by contemporary Italian standards, oodles of morbid atmosphere, and a resolution that defies happy-ending/sad-ending categorization in a manner years ahead of its time" and concluding "What keeps Castle of Blood from realizing its full potential is primarily a matter of pervasive structural awkwardness".
Images Journal calls it "the high point of Margheriti's career and one of the greatest films of the horror genre," says it is "one of the most surprising and unique films of all Italian horror" and notes:
With Castle of Blood [Italian title: Danza Macabra], Barbara Steele completed the great trifecta of Italian horror by starring in at least one movie by each of the genre's three great directors--Bava, Freda, and Margheriti. Her movies with these directors are arguably the high-point of Italian horror.