Falling asleep in this armchair draws Jack into a sometimes amusing, sometimes nightmarish dream world populated by sky pirates crewing winged sailing ships, winged reptilian "fromborks", mad sorcerers dueling in mechanical demons, tap dancing marsh wizards who assist Jack in his negotiations with the Lords of Death and more.

The nominal plot line concerns the fact that Jack unintentionally causes a mustache to appear on the lip of the Black Mona Lisa, a particularly vicious pirate originally from Philadelphia.

The final episode features an extended series of 'clips' from The Fourth Tower of Inverness as each character is seen 'dreaming' previous adventures.

After Jack first encounters a Wanted poster for the sky pirate 'The Black Mona Lisa' and causes a mustache to appear on her image as a result, he tries to hide his own identity by using the pseudonym of Marcel Duchamp.

Later he and the 'Marquis of Carumbas' are busking in the realm of the 'Never Mind' and the Marquis introduces Jack's act as Nude Descending a Staircase, another work by Marcel Duchamp.