Standing thirty yards from the Berlin Wall, Liz and Leamas wait until the beam of a searchlight stops in front of them. Then Leamas takes Liz’s arm and they move towards the wall. Leamas holds Liz very close, as if he is scared Mundt will find a way to snatch her away at the last moment. Leamas finds the spot on the wall and quickly hoists himself to the top, then leans back down to Liz and tells her to climb.
Leamas is too emotionally drained to worry much about himself, but he is acutely aware of the risks of climbing over the wall and fears for Liz’s safety. He is specifically fearful that, even though Mundt is a British agent, he may betray and abuse Leamas as he did by killing Karl Riemeck and by framing Fiedler.
As Liz begins to climb the Berlin Wall, searchlights come on all around them and Liz’s body starts to swing wildly in the air. Almost falling off the wall himself, Leamas pulls Liz towards him, when suddenly three or four shots ring out and Leamas feels Liz’s body shudder. From the other side of the wall, he hears Smiley’s voice, telling him to jump over, and asking him where the girl is.
Liz had been right when she said she knew too much to be allowed to return to England, but her death represents a final betrayal of Leamas by the organization he has dedicated his life to serving. Smiley’s involvement, however, remains ambiguous. It’s unclear whether he knew the part he played in the operation to expose Leamas as a British spy to the Germans, and whether he knows as he yells to Leamas that Liz will be killed, or if he too was betrayed by Control into going on a mission he never meant to go on.
Leamas hesitates, then climbs back to the Eastern side of the wall. He sees that Liz is dead, and looks at how her hair lies across her face. The guards seem to hesitate, but then they shoot him. The last thought Leamas has before he dies is of a small car being crashed between lorries and children waving through a car window.
Leamas realizes that Liz is dead, and his grief intensifies his feeling of connection to her. At this bleak moment, he realizes that the way that the impersonal forces of the spy services crush individuals (like trucks crushing smaller vehicles) is not tolerable to him, and that he would rather die with Liz than continue to be a part of the fight between two ideologically opposed, but equally morally bankrupt systems.