"Gretel, a lexicographer by trade, grew up on a houseboat with her mother, wandering the canals of Oxford and speaking a private language of their own invention. Her mother disappeared when Gretel was a teen, abandoning her to foster care, and Gretel has tried to move on, spending her days updating dictionary entries. When her mother phones, Gretel will have to recover buried memories of her final, fateful winter on the canals. A runaway boy had found community and shelter with them, and all three were haunted by their past and stalked by an ominous creature lurking in the canal that she called the bonak. And now that she's searching for her mother, she'll have to face it." -- (Source of summary not specified)