Whilst the book features two protagonists from his previous novel, Young Art and Old Hector, Gunn transports the characters into an allegory about totalitarianism and the nature of freedom and legend.

[1] Young Art and Old Hector are sitting in the kitchen, whilst the characters from the previous book discuss the atrocities occurring in mainland Europe.

Hector regales Art with tales of the Celtic Otherworld, the eponymous "Green Isle of the Great Deep" and of the supreme legend of the nuts of knowledge falling into the pool of life and being swallowed by the salmon of wisdom.

However, the advent of Art in the island, who proceeds to eat the fruit and then become a fugitive, causes a ripple effect which steadily causes the strict social hierarchy who live at the Seat on the Rock to slowly crumble and for God to awake.

Gunn was a Scottish nationalist and believed in small nations "being humanity's last bulwark for personal expression against impersonal tyranny.