Main •
John Benjamin Hickey as Dr. Frank Winter, leader of an initially small group of scientists working on an
implosion design weapon (loosely based on
Seth Neddermeyer and the E-5 Group at the Los Alamos Laboratory) •
Olivia Williams as Dr. Liza Winter, Frank's wife and a
botanist •
Ashley Zukerman as Dr. Charlie Isaacs, a rising young star of the Project •
Rachel Brosnahan as Abby Isaacs, Charlie's wife •
Daniel Stern as Dr. Glen Babbit, mentor to other scientists (season 1; special guest season 2) •
Katja Herbers as Dr. Helen Prins, one of the few women scientists •
Harry Lloyd as Paul Crosley,
a British scientist who wants to advance at any cost •
Alexia Fast as Callie Winter, Frank and Liza's rebellious teenage daughter (season 1; guest season 2) •
Christopher Denham as Jim Meeks, a scientist. Loosely based on the
atomic spies, in particular
Klaus Fuchs •
Michael Chernus as Louis "Fritz" Fedowitz, a scientist •
William Petersen as Colonel Emmett Darrow (season 2), a United States military officer
Recurring •
David Harbour as Dr. Reed Akley, lead scientist for the
Thin Man bomb design •
Eddie Shin as Dr. Sidney "Sid" Liao, a
Chinese-American scientist •
Daniel London as Professor
J. Robert Oppenheimer, the melancholic, somewhat reclusive, world-renowned
theoretical physicist, and scientific director of the
Los Alamos National Laboratory •
Mark Moses as Col. Alden Cox •
Carole Weyers as Elodie Lancefield, bisexual wife of scientist Lancefield •
Richard Schiff as
G-2 spy catcher Avraham Fisher (aka "Occam") •
Jefferson White as Private First Class Cole Dunlavey (aka "Iowa") •
Peter Stormare as Lazar •
Josh Cooke as scientist Lancefield •
Neve Campbell as Kitty Oppenheimer (season 2) •
Mamie Gummer as Nora (season 2) •
Griffin Dunne as Woodrow Lorentzen, a reporter and old friend of Liza Winter (season 2) == Production ==