Johnson, Daisy

Born just ten months apart, July and September are thick as thieves, never needing anyone but each other. Now, following a case of school bullying, the teens have moved away with their single mother to a long-abandoned family home near the shore. In their new, isolated life, July finds that the deep bond she has always shared with September is shifting in ways she cannot entirely understand. A creeping sense of dread and unease descends inside the house. Meanwhile, outside, the sisters push boundaries of behavior, until a series of shocking encounters tests the limits of their shared experience, and forces shocking revelations about the girls' past and future.

"Gretel, a lexicographer by trade, grew up on a houseboat with her mother. Her mother disappeared when Gretel was a teen, abandoning her to foster care, and Gretel has tried to move on. 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"--OCLC.