Published in 1981, the Codex Seraphinianus is an illustrated encyclopedia of an entirely imaginary world written in an unreadable alphabet. Hand-drawn over two and a half years by Italian artist Luigi Serafini, it has obsessed linguists, cryptographers, and art historians for over forty years. This episode steps inside its bizarre pages and the decades-long quest to decode a language that may have no meaning at all.

We explore the book's surreal visuals, from bleeding fruit to plants that grow into chairs to tools grafted onto anatomy, and how its rigid encyclopedic format makes the absurdity deeply unsettling. We examine the authentic-looking script that fooled cryptographers, Serafini's 2009 admission that the writing is asemic, and the genuine puzzles that survive that claim.

• How the script mimics real grammatical rules to tri ...