On a warm Autumn afternoon, Denmark's largest amusement park, Tivoli Gardens, is devastated by a terrorist attack that leaves more than 1,200 dead. No one claims responsibility for the attack, and seven months later the nation is still reeling and the police have no leads. Police Lieutenant Lene Jensen has been assigned to the frustrating case from the beginning. When she receives a desperate phone call from a Muslim woman who later turns up dead, she sees a connection to the Tivoli bombing. Lene's initial investigation suggests that the woman was unknowingly part of a secret research project conducted by the government, and as she digs deeper, she is met with increasing resistance from her superiors. Together with private detective Michael Sander, she tries to get to the bottom of the complicated case--only to realize that someone knows a lot more than they are letting on. With the threat of another attack looming, Sander and Jensen must race against the clock to save lives and restore peace of mind to the people of the idyllic country.