During the whole of The Spellcoats, the events surrounding the death or loss of their mother trouble and affect the children of Closti the Clam, but none of them know quite how to frame their confusion or their feelings about her.
While they are traveling down the River, fleeing their former home in the village of Shelling, their hearth statue of The Lady is carried by the youngest, Duck. Sometimes, when their war-damaged brother Gull is raving and unhappy, he gives it up to Gull to carry, and it seems to comfort him. Duck sometimes says that the statue grows warm, and that is how he knows his Mother is with him, but no one else believes him, Tanaqui because she feels he lies very easily, and Hern because he has decided not to believe in the Undying.
By the last third of the story, connections between the Undying and the family seem to be proliferating in some way. Tanaqui continues to have dreams of her mother -- at first saying "watersmeet" but recently saying "Think, Tanaqui. You need to think."
After seeing one of Kankredin's evil mages speaking furtively with Shelling village headman Zwitt across the River, Tanaqui watches him catch sight of her finished Rugcoat -- the one she's been weaving with their story in runes the whole time Robin was lying in their new camp in the old Mill, recovering -- and stare at it with horror, as if he can read parts of it and it makes him afraid. Tanaqui suddenly puts many things together and rushes around to ask her siblings what they vowed to the Undying, and demands of Duck what he's done with Mother. Duck is outraged at the request and at the fact that she seems to know their mother is in the statue, and as they are fighting, a beautiful young woman walks into the the room, scolding the two of them lovingly for making such a noise.
This is Anoreth, their mother, who proceeds to tell them many things about their history that they didn't know or partly guessed. That their father had put her soul into the Lady when she was about to die after giving birth to Duck; that she had been the woman haunting the Mill when their father was a boy; that when he was grown, she took shape and walked up to him saying "My name is Anoreth, will you marry me?" And she says that she took the shape of the statue so she could look after them, that Tanamil is one of the Undying but not a relative -- he was bound to the statue after creating the river that ran into the larger river that The One had created.
Tanaqui tells her she thinks Robin is in love with Tanamil, and her mother agrees. She explains to Tanaqui how to call him, and then leaves to speak to Hern. From this point in the novel, things get very supernatural very fast.