1939, war approaches England, and witchery is afoot.

Eliza MacLean is descended from witches, yet forbidden to follow the craft by her domineering mother on the Isle of Mull. Taught in secret by her grandmother, Eliza learns about healing herbs and spells, but her true strength lies in her psychic abilities. She can converse with spirits and find the missing. A confused Eliza struggles with an uncertain future, but is devastated by the sudden death of her gran, and her whole world crumbles.

Her prescient gran foretold the coming war and as Eliza escapes to Cambridge she is coaxed into the craft by her wiley cousin. In Cambridge, a wide network of witches, all working to prevent the German invasion. Eliza is recruited by MI5 to find a German spy, but in facing their new enemy, they could be closer than she thinks.