In 1961 Berlin, as the Wall goes up dividing the city, swimming champ Harry Melchior escapes to East Berlin. Living in West Berlin with friends and fellow escapees, Harry devises a plan to get his sister Lotte and others over to them. His group decides to dig a huge escape tunnel underneath the Wall. As the project gains momentum, more people join the effort and more plan to escape. Over the year it takes to build the tunnel, pressure continues to mount on both sides of the Wall.