"I am the korrigez who founded Ys, both above and below the waves... and now I am here to take back what's mine and lay waste to what never should have been built!" [loc. 4508]
Nolwenn and her family are lighthouse keepers, defending the city of Ys. They use lenses to focus the moon's rays, to kill teuthes -- great monsters from the deep -- that threaten the sea-defences. She's been lucky, finding seasilk (a rare and precious commodity that can protect against the black tide) and is summoned by the queen, who flirts with Nolwenn and tells her to fetch enough seasilk to provide shield-nets for the lighthouses as well as the city.
Nolwenn recklessly rows out one night and is attacked: but she's rescued by a merperson, a korrigez who she names Morvan after the chieftain in a popular serial. Morvan takes Nolwenn to Ys-below, a coral palace deep in the ocean: she learns a lot (some of it rather uncomfortable) and falls in love, but yearns for her family, for sunlight, for air.
The worldbuilding is a delight: I loved the reimagining of the Breton folk tale about a city drowned by the sea. The half-humanoid, half-fish korrigez (Breton for 'mermaid') are fascinating, as are the ecology and economy of Ys-below. Coral for communication! Wiesebron is a marine ecologist and admits in her afterword that 'the fantasy of suddenly sprouting fins is one that I enjoyed, albeit from the safe and dry distance of my pen and paper' [loc. 4923] And I loved the resonances with the in-universe fiction 'Leylou Among the Korrigez'.
But I do think this novel could have done with another edit. There are pacing issues: the first third of the book is really slow, and the last third feels rushed. There are typos and infelicities: 'discretely' instead of 'discreetly', 'it's' instead of 'its', someone knowing something and a few pages later not knowing it. And Nolwenn, though she's twenty-three, sometimes behaves like a much younger girl: she's prone to impetuous behaviour, and doesn't always know the rationale behind her own decisions.
Really interesting setting, slightly disappointing prose -- but there's a fascinating romance, and a suitably epic finale.
Thanks to the publisher and Netgalley for the advance review copy, in exchange for this full honest review. UK Publication Date was 21st May 2026.





