In the season finale of "Manhattan" season 2 titled "The World of Tomorrow," Frank met Charlie and tried to justify himself.
However, Charlie was not in a mood to hear him and pushed him out of his home. The military soldiers were waiting for Frank outside the house and arrested him immediately.
Col. Emmett Darrow was waiting for Frank when the soldiers dragged him in. Instead of locking him back in his cell, Darrow showed him a classified file about the war.
Darrow told Frank that he must abide by his rules if he ever wants to work on the project again.
Elsewhere, Woodrow had started the interview process while Frank told him that how he became friends with his daughter's boyfriend. As the two eventually became friends, Frank shared his cigarettes and borrowed Woodrow's lighter.
Frank was infuriated when Darrow sent a young soldier to battle in the most violent foreign soil, but it was not under his authority to stop it.
Jim and Louis were interviewed by Woodrow. Meanwhile, with the help of Paul, Frank found a way to get back to tech and watched how the team was doing with the equations.
Charlie took Jim and Louis into the desert for the next test. While practising on the desert soil, a group of cowboys visited them who were carrying guns.
One of the cowboys pointed his gun at Charlie's head while Frank tried to convince them not to shoot anyone. Agreeing to the points made by Frank, the cowboys finally decided to leave.
However, it didn't go well with Charlie and he had a fight with Frank. He told Frank that he doesn't need his help and promised him that Frank will never be a member of the tech group till he is around.
At the end of the episode, Frank came to know that the young boy who was sent to battle had died and he was none other than Woodrow's daughter's boyfriend.