During a military exercise on Gotland, thousands of soldiers are mobilized on the island. A sudden explosion occurs in a military protection area and a young soldier loses his life. Maria Wern and her colleagues are involved in the case, but the military is more secretive than expected. What is really behind the explosion? The Gotland police also get a new addition: Sasha who has a background from military service abroad - something that raises thoughts within Maria and makes her start to doubt if she is in the right place in life.