"The Half Brother" is a sweeping family drama set against the backdrop of 20th-century European history. On V-Day, May 1945, as World War II ends, Vera Nilsen is raped in her Oslo attic by an unknown man, leading to the birth of her son, Fred. Five years later, Vera marries and gives birth to Barnum, dividing the Nilsen family, much like Europe, into two. Raised during the Cold War, the half-brothers grow apart, with Fred embarking on a quest to find his biological father and ultimately vanishing. At the 1990 Berlin Film Festival, coinciding with the fall of the Berlin Wall, Barnum discovers Fred's return. As the truth about Fred's father comes to light, the half-brothers may finally reunite.