The countdown to the first nuclear weapon test goes on, as Frank Winter races to apprehend a Soviet spy who intends to sabotage the gadget. The scientists from the hill withdraw from the Trinity site to witness history being made.

Days before the world's first nuclear explosion, everyone races to secure their place in history.

As the project falters, Charlie turns to an unlikely partner for help.

The hunt for a Soviet spy turns deadly.

The scientists and the Army battle for control of the bomb.

Frank tries to navigate his new place on The Hill.

Frank's situation improves with unexpected aid. Oppenheimer's private life has unforeseen impact on project.

Liza faces off against Darrow as Abby learns a secret about Oppenheimer.

Frank discovers the real reason he's been taken captive.

Charlie is forced into a new leadership role in the race to build the world's first atomic bomb.

Frank is given a life-changing opportunity, while Charlie finds himself in the US Army's hotseat.

Akley becomes vulnerable when he tries to fix Thin Man's shortcomings.

A development overseas re-invigorates the hunt for a spy on The Hill. Charlie and Abby make a sacrifice when the plan with Frank is threatened.

Charlie and Frank are forced to work together for the good of the project. When they run into a problem, Frank turns to an unconventional resource.

Charlie and Frank both face serious questions about the future of their projects.

Helen and Charlie must solve a crisis at the reactor. Frank and Liza help Paloma's family. Abby begins a journey of self-discovery.

Frank seeks medical answers. Charlie and Helen travel to survey an off-site reactor.

When Babbit's past comes back to haunt him, Frank clashes with Charlie to protect his mentor.

When Babbit's past comes back to haunt him, Frank clashes with Charlie to protect his mentor.

The community reels after losing a member, while new security measures affect the scientists' work.

Frank's attempt to save his team brings serious consequences. The scientists' wives find creative ways to survive life on The Hill.

Charlie Isaacs and his family arrive in Los Alamos and attempt to navigate a community built on secrets. Frank Winter, the head of the Manhattan Project, struggles with the sacrifices he is making to help the U.S. win World War II.