The shadow has waited for mourning to weaken her. It wears the faces of everyone she has lost, and it wants the sentient Cornish cottage she is sworn to guard, the living threshold between worlds that only a Trevelyn can hold. If grief opens a single crack in her, the threshold falls with it.
She has one afternoon, one door, and the only instrument that has never failed her: she paid attention to the ones she loved.
The shadow spent a year learning her grief. She spent a lifetime learning him.