 The script is by Rae Brunton, based on Parker's original concept, which he described as ""Platoon" meets "The Sixth Sense"".Although set in Eastern Europe, filming was done in the ruined WWII Edingham Munitions factory near Dalbeattie, in a forest on the Balmaghie estate near Castle Douglas, and in the Glasgow Film City studio complex in the Govan area of Glasgow.Filming began in January 2007.