Campbell Scott

Self - Narrator (voice)

Boyd Gaines

Chairman Gray (voice)

Daniel Gerroll

Colonel Pash

Michael Stuhlbarg

Edward Teller

Ellen Katz

The Stenographer

Michael Cumpsty

Harold Agnew

Self

Jeremy Bernstein

Self

Freeman Dyson

Self

Richard Rhodes

Self

Martin J. Sherwin

Self

Joseph McCarthy

Self (archive footage)

J. Robert Oppenheimer

Self (archive footage)

David Strathairn

J. Robert Oppenheimer

Herbert York

Self

Marvin L. Goldberger

Self

Priscilla McMillan

Self

Robert Christy

Self

Roy Glauber

Self

Harry S. Truman

Self (Archive Footage)

J. Edgar Hoover

Self (archive footage)

Lewis Strauss

Self (archive footage)

Dwight D. Eisenhower

Self (archive footage)

Eleanor Roosevelt

Self (archive footage)

Edward Teller

Self (archive footage)

Lyndon B. Johnson

Self (archive footage)