Seventeen-year-olds Kati (Anna Maria Mühe) and Steffi (Karoline Herfurth) are best friends. But while Steffi has a great boyfriend and a loving home, Kati is lovelorn amid her family's incessant squabbling -- but the tables are about to turn. Kati discovers that Steffi's father is having an affair, and as Steffi's perfect world falls apart, the girls try to find out all they can about her father's new lover.