Plot

A French gentleman, notorious for his secret identity as Le Chevalier Noir ("The Black Knight"), the world's greatest cat burglar, comes to Duckburg to test his skills against Scrooge's Money Bin. Even with Scrooge and his nephews on high alert, the thief has little trouble entering into the bin and its innermost vault. As a souvenir of his triumph, he takes a few choice items from Scrooge's office.

Later, however, he is disappointed as he examines his trophies: a suit of medieval armor, a bag of diamond dust (swept from the floor of a local jeweler), and a solid diamond jar filled with black goop. Upon closer examination, he identifies the goop as "Omnisolve", the universal solvent invented by Gyro Gearloose

Gyro Gearloose

Gyro Gearloose is a fictional character, an anthropomorphic chicken created by Carl Barks for The Walt Disney Company. He is part of the Scrooge McDuck universe, appearing in comic book stories as a friend of Donald Duck, Scrooge and anyone who is associated with them. He was also a frequent star...

 (and previously featured in the comics story of the same name

The Universal Solvent (comics)

-Plot:Gyro Gearloose has invented a "universal solvent", a thick, black liquid capable of instantly dissolving anything except diamonds, with it then transforming the dissolved matter into a super-dense dust. Gyro then gives the Universal Sovent kept in an diamond jar and a Omnisolve beach umbrella...

). With some calculation, the Black Knight plans an even bolder assault on the money bin: by applying the diamond dust to the suit of armor, he is able to coat the suit (except for the palms of its gauntlets and the soles of its shoes) and the blade of its sword in the Omnisolve, allowing him to march into the bin in broad daylight.

None of Scrooge's security measures are able to stop the Black Knight, as the solvent instantly dissolves everything in its path, including bullets. When the Black Knight reaches the door of the vault, Scrooge challenges that he won't be able to steal all of McDuck's money at once. The Black Knight says that he will be satisfied simply dissolving all of Scrooge's money out of existence, thus creating the illusion that he did in fact manage to steal Scrooge's entire fortune. Desperate, Scrooge realizes how to defeat him: by pulling a rug out from under his feet, tipping him onto his back, where he falls down through the many floors of the bin.

Luckily for the Black Knight, his fall is broken by the contents of Scrooge's diamond vault, and the impact knocks him senseless. Scrooge and Co. gingerly remove him from the armor. The Black Knight graciously admits defeat, and agrees to leave the room handcuffed, presumably to be taken into police custody. However, he quickly escapes his cuffs and disappears, leaving a note promising to return one day.

Background Information

This story was a sequel to Rosa's story "The Universal Solvent

The Universal Solvent (comics)

-Plot:Gyro Gearloose has invented a "universal solvent", a thick, black liquid capable of instantly dissolving anything except diamonds, with it then transforming the dissolved matter into a super-dense dust. Gyro then gives the Universal Sovent kept in an diamond jar and a Omnisolve beach umbrella...

", and was likewise followed by "The Black Knight Glorps Again".