12 years ago policewoman Lena Jörning last heard from her sister Evelyn, who left the small village on the Baltic coast of Germany in order to escape from the monotony of everyday life. When a body is found in the frozen Baltic, Lena has to take charge. It comes as a terrible shock to her when she understands that the first corpse in her career she encounters turns out to be her own sister. A team of CID officers arrives to take charge of the case. Plenty of questions need to be clarified: when did Evelyn return, and why has Lena not known anything about it? Do Evelyn’s husband Claas and Lena’s fiancé Bruno have anything to do with the case? The investigation becomes a dramatic journey into the past for everybody involved, a past which – although Lena hasn't been able to recognize it - still overshadows the present for the entire village.