On the morning of Eva McEwen's birth, six magpies congregate in the apple tree outside the window-a bad omen, according to Scottish legend. That night Eva's mother dies, leaving her to be raised by her aunt and heartsick father in the small town of Troon, Scotland.

As a child, Eva is often visited by two companions: a woman and a girl. Invisible to everyone else,

they seem benevolent at first, helping her to tidy her room and collect the hens' eggs. But as she grows older, their intentions become increasingly unclear: Do they wish to protect or harm her? Is their meddling in her best interest or prompted by darker motivations?

In the shadow of World War II, Eva studies nursing in Glasgow, tending to the wounded soldiers. But when she falls in love with a young plastic surgeon, the companions seem to have a very different idea as to her fate, and once again she finds herself unable to resist their pull.