Adolfo Verybad, the scientist who is as odd as he is ingenious, has created a serum that makes whoever drinks it temporarily invisible. Jim Kelly, the runaway, has gotten hold of it and uses it to carry out thefts and murders. Zagor captures Kelly, but the soldiers of Fort Jericho want to use Verybads serum for military purposes. Indignant, the King of Darkwood decides to make a clamorous gesture