In The Wall of Serpents, Shea visits his fifth such world, that of the Finnish mythological epic poem the Kalevala.

When Harold Shea's wife Belphebe, originally from the world of Spenser's The Faerie Queene, was accidentally spirited off to that of Ariosto's Orlando Furioso (The Castle of Iron), he came under suspicion by the police for her disappearance.

While he was ultimately successful in retrieving her, two others, his colleague Walter Bayard and policeman Pete Brodsky were left trapped in the world of Coleridge's Xanadu.

As Shea's skill in traveling between universes is still somewhat hit or miss, he decides to seek professional assistance in rescuing them, from the wizard Väinämöinen in the world of the Kalevala.

Later, after their quest with Lemminkäinen to Pohjola goes sour, Bayard inadvertently transports them to the world of Irish myth.