When Mercy Helsing is convicted and sent to an Immortal prison deep in the Arctic Circle, she doesn't expect to survive longer than a day.Thrown into the depths of the icy fortress, she's forced to fight for her life again and again in terrifying trials. But Dodstarn is nothing like she expected, and she soon finds unlikely friends amongst the fierce convicts. And the man she entered the prison with has her back in every test she faces. But when girls start being murdered in the prison, Mercy has to work fast to figure out who her enemies are. Before the killer turns their attention to her...