Connie has one chance to enrol at the mysterious fortress of Blackwood to become a Caster. There, she will be trained to navigate the dark and battle the spectres that live in the Shade, a terrifying, malevolent darkness that is rapidly expanding and threatening to engulf the ordinary world. The soldiers of Blackwood are ruthlessly trained to hold the borders of the light – and this is her only shot at becoming one of them.

But every Caster needs a Seeker, and when Connie is paired with the aloof and sarcastic Jasper, their dislike is mutual. If they are to have any hope of resisting the encroaching darkness, they must learn to depend on each other.

For when the vows fail, the light fails too.