The ghost of Ludwig von Strangeduck arrives and signs in as a guest. The appearance of the ghost doesn't prompt the guests (the Duchess and Benzino) to leave the hotel. The nephews suspect foul play and start investigating. They discover that Strangeduck has no grave in the cemetary.
The Duchess of Swansylvania, one of the hotel guests, wanders around looking under pictures and examining the walls. The Duchess discovers a secret door and Scrooge discovers that it leads to a secret room, where the nephews find a can of invisible paint. It's revealed later that she is the sister of Dr. Strangeduck, who is trying to keep his old lab assistant from discovering the book containing all of his secret formulas, which could be worth millions of dollars.
Dr. Strangeduck is an old Disney character who appeared in the comics and has appeared in subsequent Disney cartoon shows.
It's a cute moment when the nephews ask Scrooge for a tip, which he promptly takes back as management cut.
The scene with Scrooge, Duckworth, and the nephews fighting the ghost at the door of the hotel is really exciting. I like how the fight takes place on an invisible drawbridge.
This is a great episode full of mystery and intrigue. Is the ghost real? What is the duchess looking for? What mysteries does the castle hold? Great story from start to finish.