Top positive review
Toby levels up
Reviewed in the United States on December 13, 2021
One Salt Sea is the fifth book of Seanan McGuire's October Daye series. The previous book, Late Eclipses, was a big breakthrough that revealed a lot of new information about Toby. We learned that Toby's mother, Amandine, is not actually Daoine Sidhe as Toby believed. Amandine is one of the firstborn, meaning her father was fairy god Oberon. (I call him a god because the fae literally swear by him, as we would say "By God", they say "By Oberon".) That makes Amandine's descendants a new race, the Dochas Sidhe. Currently there are, aside from Amandine herself, only two Dochas Sidhe: Toby and Toby's unfortunate daughter Gillian. Toby's father was human, making her a half-fae changeling. Gillian's father was also human, so she is a quarter-fae changeling.
In the very first book, Rosemary and Rue, we learned that a changeling is not necessarily a changeling forever. Oberon created magic artifacts called Hope Chests that can make a changeling into a pureblood. We also learned in Late Eclipses that Amandine is a kind of a living Hope Chest -- she can, through her personal blood magic, modify a person's inheritance. She did this to rescue Toby after Toby was poisoned with elf-shot, which would kill a changeling. At the same time, she gave Toby an upgrade, not to full pureblood status, but to greater magical strength and power.
The hero of One Salt Sea is thus a new Toby, Toby 2.0, with greater abilities and stronger magic. Fortunately, her sarcasm superpower is backward-compatible. And we have the feeling that Toby doesn't yet know all the new stuff that got installed with the 2.0 upgrade.
The story takes off when it is revealed that the two sons of Dianda and Patrick Lorden, the Duchess and Duke of Saltmist, have been kidnapped. Saltmist is an undersea realm -- Dianda (the ruling monarch) is a Merrow = mermaid, while her consort Patrick is Daoine Sidhe. Dianda and Patrick suspect that the Queen of the Mists, head honcho of the San Francisco Bay Area Fae, has a hand in the kidnapping. Dianda declares war. Fae legalities require a three-day notice on declarations of war, so Toby has three days to find the kidnapped boys and prevent the war.
Thus Toby has a mystery to solve, and in this book, like some but not all novels in the series, solving the mystery is most of the plot. It's not a bad little mystery, and Toby gets to be a little bit clever, so that's good. I liked this book mainly because of its further exploration of Toby's world and her abilities.