Armin works as a proofreader for a scientific publishing house. He has a son, Bo, with his first great love Monika. He now lives with Ellen, his late wife's best friend and they want a child together. Then, 13 years after the birth of his son, he discovers that he is and has always been infertile. So his son cannot be his son. The only one who can point out the father with certainty is his son's mother, but she has been dead for 10 years. He must rethink everything he has believed about himself and his life all these years. Furious, jealous and disillusioned, he decides to look for his son's father. During his search through the past, he relives everything.