I see a lot of praise heaped on this is some of the other reviews and I have to wonder how much of that is based on the idea that Welles was frequently behind the camera and taking the lead.
That is the case and it often shows. Welles style and eye can be seenbat several points during the film. Unfortunately this in and of itself does not ultimately make this a good film. It is very much a product of the assembly line era that it came from.
Take out Welles contributions which in certain scenes give us great shots and what you have is a completely forgettable period piece with a convoluted story that overstays its welcome in terms of length. The film feels too long, yet does not do enough with its running time. Here is Cagliostro the boy, here is Cagliostro the man, here is Cagliostro the toast of high society... all in the blink of an eye, with the only exculpatories being some montages of mass healings. Poor and rushed storytelling, only to hurry up and wait when Cagliostro happens upon the man whom he has sworn to never forget, and the rather tedious and drug out revenge plot takes over.
Nothing I say will stop anybody from watching this, and that's a good thing, you should watch it. It is an interesting bit of the Orson lore, but don't expect the "lost classic" or a "hidden masterpiece". It is neither of those things.
