When nine­teen-year-old Doris mar­ries Rob in 1941 and has a sick­ly, pre­ma­ture baby, she trades in her dreams of becom­ing a con­cert pianist or lawyer to becom­ing the ide­al wife and moth­er. With­in months of their daughter’s birth, Rob is recruit­ed to work on the Man­hat­tan Project. The young fam­i­ly moves to Oak Ridge, Ten­nessee. Like fis­sion splits an atom’s nucle­us, Doris’s mar­riage threat­ens to break her heart in two. She strug­gles to nur­ture her daugh­ter while Rob works around the clock. In search of con­nec­tion, she befriends Bet­ty, a South­ern debu­tante. Despite their dif­fer­ent back­grounds, the two women sus­tain each oth­er through var­i­ous trau­mas: Betty’s mis­car­riage, Rob’s radi­a­tion expo­sure, and his attempt to enlist to fight at the front. Although Doris tries to make life in Oak Ridge work, she falls for an army engi­neer — only to real­ize that he may be a Sovi­et spy. Should she turn him in and risk ruin­ing her mar­riage? As the end of the war nears, Doris must decide what’s most impor­tant — and what she’s will­ing to lose.