Eifler is in Algeria (this is where the Office of Strategic Services is, apparently) contemplating his plan to kidnap Heisenberg.
OSS director General William Donovan shows up and tells him that his mission has been scrubbed because they've already won the atomic bomb race.
Eifler is, well, let's just say bummed would be a massive understatement—he's convinced he won't get the last guy he killed out of his mind until he kills someone else. (Sounds like he might be a little unhinged).
In reality, Donovan just wants to take Eifler off the mission without hurting his feelings. (Too late?)
The mission to kidnap Heisenberg is still a go, but now it will be led by an ex-ballplayer named Moe Berg.
Moe Berg has been involved in a secret operation called "Alsos," which follows close behind advancing Allied forces in Europe and collect scraps of information about the German atomic program.
Since he's there, and has a background in physics and languages, he's been selected to render Heisenberg "hors de combat" (which is French for "out of the battle") during a scientific conference in Switzerland—a phrase which is a bit too vague considering the circumstances.
After the war, he admits to a fellow secret agent that his orders in the "Swiss Deal" were to shoot Heisenberg—right there during the conference—if he was presenting anything that would intimate that the Germans were close to having an atomic bomb. It would have been controversial and basically a suicide mission.
So Moe Berg poses as a Swiss student who's psyched to hear the great Heisenberg lecture about physics. He enters the conference with a pistol in one pocket, and a cyanide tablet in the other.
Heisenberg lectures on advanced mathematical theory, so Berg doesn't really know if it's related to an atomic bomb or not, and in his confusion decides not to kill him.
A few days later, though, Berg finds himself at a dinner party with Heisenberg. Small world, eh?
When people start angrily asking Heisenberg how he could possibly fight for Nazi Germany, Heisenberg admits that Germany is pretty much defeated. His resignation to losing the war convinces Berg that the Germans aren't on the cusp of creating an atomic bomb, and based on this evidence, he doesn't kill Heisenberg.