Apuleius' Metamorphoses (or The Golden Ass), a masterpiece of Latin literature from the second century AD, still captivates modern readers with its combination of asininity and mysticism. In the novel, a young man named Lucius tells how he accidentally turns into a donkey and then describes how he regains human form with the help of the Egyptian goddess Isis, into whose cult he is initiated. This book argues that invisibility is one of the central motifs in the Metamorphoses and, in the process, presents a new interpretation of Apuleius' novel as a visionary, esoteric text. It contributes both to the study of the subtle relationship between literature and Platonic philosophy and to the cultural history of invisibility in classical antiquity and beyond.