On a visit to his childhood home to look in on his mother, famous playwright Robert Longfellow (Martin Donovan) is taken hostage by Gus (David Morse), an ex-con neighbor he has avoided since he was a boy. As the drama unfolds on the cable news channels, the two men unexpectedly bond until the mood darkens and shots ring out.

A Mystic's daughter flees Moscow on the eve of the Great War. A French soldier lies wounded on the Western Front. A German officer veers between loyalty and integrity. An English courtesan reclines on a sea of books. Each will make a journey that changes history. The constellations will force the Mystic's daughter to make an impossible choice. To remain at her harp as the shadow of the war looms again – or join the top-secret Special Operations...

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

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

A new era is ushered in with the first test of an atomic weapon.

Set during WWII in Los Alamos, New Mexico, secrets dominate every facet of family and professional life as scientists Frank Winter and Charlie Isaacs compete to create the world's first atomic bomb.

The hunt for a Soviet spy turns deadly.

The scientists and Army battle for control of the bomb.

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

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