November, 1967, Iceland. Fourteen-year-old Marsi has a secret penpal – a boy who lives on the other side of the country – but she has been writing to him in her older sister’s name.

Now she is excited to meet him for the first time. But when the date arrives, Marsi is prevented from going, and during the night her sister Stína goes missing – her bloodstained anorak later found at the place where Marsi and her penpal had agreed to meet.

November, 1977. Stína’s disappearance remains unsolved. Then an unexpected letter arrives for Marsi. It’s from her penpal, and he’s still out there… Desperate for news of her missing sister, but terrified that he might be coming after her next, Marsi returns to her hometown and embarks on an investigation of her own.

But Marsi has always had trouble distinguishing her vivid dreams from reality, and as insomnia threatens her sanity, it seems she can’t even trust her own memories … and her sister’s killer is still on the loose…