Character vs. society: Gerta is trying to escape East Berlin which is against the rules and against what people think is possible. She is challenging the beliefs of society.
Gerta sees her father on the other side of the wall one day and he motions to her to dig where she is standing. He then sends a picture through a former friend of hers showing what building to dig in for the treasure. She begins digging and finds an air raid shelter and gets her brother involved in digging under the Berlin wall.
They set up an elaborate disguise to conceal their true intentions, saying that they are making a flower bed for their mother. They set up a clothes line near the pond and use this to hide part of their work site. They have to hid it from everyone, their neighbors, their friends, even their mother
Officer Müller is suspicious and makes an outside inspections, being moments away from discovering their digging. Later Müller finds them in their tunnel and they convince him to bring his wife and baby along to escape, which he agrees to.
Gerta figures out that Anna knows about the tunnel but hasn't said anything. Gerta has to retrieve a door from a higher level on the building, and almost gets caught by the guard tower lights. They involve their mother in digging and hear someone digging on the other side, which turns out to be their father.
Their father's tunnel is slowly collapsing and soldiers come to collect Fritz for his military assignment so they all get to the tunnel and find Anna and her family, and Müller and his family. They start crossing and an officer above digs in stopping Gerta and Müller, so Müller reaches out to grab the gun, gets shot, as he sends Gerta through to the other side of the tunnel. Müller is shot but eveyone else gets through.