Sisters of salt and iron

"The spirit of Wren Noble is lonely even though she talks with her living twin sister Lark. Then Wren meets Noah, the spirit of a young man who died a century ago. But Noah has a dark influence on Wren and Lark's distrust of him drives the sisters apart for the first time in their lives. As Halloween approaches, Lark must find a way to stop whatever deadly act Noah is planning, even if it means going through her sister to do so."--Provided by publisher.