Halley Ashwood is well on her way to achieving her dream of becoming a doctor. Focused and independent, with a mother she never knew and a father who never loved her, the only constant Halley has ever had is her brother, Flynn. Whilst Halley is logical and grounded, and Flynn a reckless conspiracy theorist, they have always been able to trust each other above anything else. The Ashwood siblings don’t believe in making promises. So when Flynn leaves Halley a message the day before her scheduled trip to visit him in Amsterdam, asking her to promise him she won’t come, she knows something is wrong. Halley arrives in Amsterdam to find her brother missing, leaving only those ominous words in his wake. Halley sets out to investigate what happened to her brother and makes a terrifying discovery. Turns out Flynn’s conspiracy theories weren’t so farfetched after all: demons are real, they’re stalking the streets of Amsterdam, and they may hold the answer as to what happened to Flynn. Determined to find out the truth about her brother’s fate, Halley embarks on a dark journey that will force her to question everything she thinks she knows about the nature of the world, the forces within it, and even herself.