The Old Castle's Secret is a 32-page Disney Ducks adventure/mystery story, written and drawn by Carl Barks and first published in June 1948. A surprisingly dark and moody story for a Disney Funny Animal comic - as reflected in the artwork - it's remembered for being the second appearance of Scrooge McDuck in a proper comic, and the first of many "Treasure hunt" stories the ducks would get involved with in subsequent years.
Rich old uncle Scrooge McDuck is in dire financial straits, and needs to recover his family's ancient treasure, a jewel box hidden in the 11th century by his ancestor Sir Quackly. The treasure is hidden somewhere in Castle McDuck, upon Dismal Downs in Scotland. Moreover, rumor has it that the ghost of Sir Quackly dwells within the castle walls, looking over his treasure. Fortunately, Scrooge has commissioned an X-ray machine that will allow the ducks to scour the inside of the castle walls, where the treasure is said to be hidden. Apparently, Sir Quackly sealed himself inside the castle walls with the treasure in 1057, but neither he nor the treasure were ever seen again. The castle's caretaker, Scotty McTerrier, jumps to help with the treasure hunt, and the treasure is soon found sealed in the walls near Sir Quackly's remains. Unfortunately, it seems the ghost is very interested in keeping the treasure sealed away, and the ducks find themselves up against an invisible menace hell-bent on keeping his ancient jewels...
This story has examples of
- Early-Installment Weirdness: Aside from his somewhat odd appearance, Scrooge is a good deal more timid than he'd show himself to be in later installments, and he mentions that he urgently needs a few million dollars to keep his fortune - a far cry from the indescribable wealth he'd later be shown to possess.
- Forgotten Phlebotinum: Diamond Dick's invisibility spray. He mentions getting it off a spy, suggesting it's considered very rare, but we never see anyone else using it again in subsequent comics, even when it would have come in very handy. Granted, it's treated as something unprecedented in-universe, so whatever happened to the inventor/s is open to debate.
- Ghostly Goals: The ghost intends to keep his treasure secure, and doesn't care who he has to hurt to do it.
- Haunted Castle: Castle McDuck certainly counts, and the ghost doesn't seem too keen on allowing people to abscond with his treasure...
- Idiot Ball: After being locked out onto a battlement by the ghost, the ducks realize they could very well be trapped. The kids manage to swing into the moat, but then realize they're locked out of the castle. Only then does Scrooge remember he has a gun, and can use it to shoot out the lock and free himself. To his credit, he admits this was pretty stupid on his part.
- Invisible Jerkass: The ghost. He doesn't hesitate to stoop to attempted murder going after the ducks.
- MacGuffin Guardian: Sir Quackly's ghost seems to be this for his jewel box, keeping it away from others seems to be his sole motivation.
- Multilayer Façade: Diamond Dick spends most of the comic pretending to be Scotty McTerrier, but can also use the Invisibility spray to take on the role of Sir Quackly's ghost.
- Not So Invincible After All: The invisible ghost has been running rings around the ducks for the last several hours - until Scrooge fires a couple bullets at it, at which point the ghost turns and flees, hinting that there's something more going on.
- Our Ghosts Are Different: Sir Quackly is invisible, but very strong, tangible, and can manipulate objects around him. In a direct light source, the shadow of a human skeleton can be seen wherever he is. Justified, since he's not actually a ghost.
- Quicksand Sucks: Downplayed near the end; it's enough to slow the ghost down quite a bit as he tries to flee, but the pool isn't deep enough to completely suck him under.
- "Scooby-Doo" Hoax: It seems the "ghost" was a noted jewel thief named Diamond Dick, who disguised himself as Scotty McTerrier, who died several months ago and has been looking for the treasure ever since. He made himself invisible by using an "invisibility spray" he picked off a spy during the war. It was imperfect, though, since in a strong light source, the shadow of the person's bones could still be seen, and it wears off after a short time.
- Secret Underground Passage: The kids find one that leads from Sir Swamphole McDuck's grave in the cemetery to the castle's dungeons.
- Treasure Hunt Episode: The first of many - finding the treasure actually isn't particularly difficult this time, it's keeping it that's the hard part.
- X-Ray Vision: Scrooge has commissioned a prototype X-Ray machine that allows him to look through walls. It's big and bulky, but it allows the ducks to sweep the castle and find Sir Quackly's treasure chest relatively quickly.
