Eleanor Schiff is a sev­en­teen-year-old high school stu­dent liv­ing with her fam­i­ly in Philadel­phia. The year is 1942, and the Schiffs are anx­ious about their rel­a­tives in Poland. The Joint Dis­tri­b­u­tion Com­mit­tee is report­ing about vio­lence against Europe’s Jews, at a lev­el worse than the pogroms of the past. Amer­i­cans are now in the war, but an Allied vic­to­ry is still in the future. Eleanor’s idol is the First Lady, Eleanor Roo­sevelt. Like her famous name­sake, young Eleanor is often plagued by self-doubt and needs to remind her­self to take chances. When a bril­liant math­e­mati­cian, Mary Mauch­ly (a real his­tor­i­cal fig­ure), recruits Eleanor for a secret pro­gram at the Uni­ver­si­ty of Penn­syl­va­nia, the gift­ed stu­dent is con­flict­ed. She learns to cal­cu­late the risks and ben­e­fits of serv­ing her coun­try in a high-pres­sure pro­gram, and finds her own path forward.

Com­pli­cat­ing the equa­tion for Eleanor is a secret she has car­ried with her from ear­ly child­hood. When her father, a pro­fes­sor of math­e­mat­ics, suf­fered a dis­abling stroke, Eleanor blamed her­self for the tragedy. The genius she has inher­it­ed from him has become a bur­den, forc­ing her to take the cir­cuitous route of pre­tend­ing she is actu­al­ly inept with num­bers. When she acci­den­tal­ly leaves her note­book — a kind of Cinderella’s glass slip­per — at the Penn­syl­va­nia State Math Meet, Mary Mauch­ley returns it to her. Instead of pair­ing her with a prince, Mary gives Eleanor a role in the Philadel­phia Com­put­ing Sec­tion, where female ​“com­put­ers” will ensure the accu­ra­cy of US bal­lis­tics. Although the author incor­po­rates actu­al equa­tions and care­ful descrip­tions of the project into the book, her real focus is on Eleanor and her col­leagues, who are all young women liv­ing away from home in a secret envi­ron­ment. The sto­ry, which is full of ten­sion, com­pe­ti­tion, and cama­raderie, has the thrilling authen­tic­i­ty of a 1940s movie. Eleanor encoun­ters anti­semitism, while her friend Alyce, who is Black, con­fronts racism.

Eleanor’s insight into cal­cu­lat­ing the tra­jec­to­ry of a shell sends her to a mil­i­tary base in Cal­i­for­nia, where she is direct­ly involved in per­fect­ing the accu­ra­cy of the Nor­den bomb­sight device. There, she becomes attract­ed to a pilot from Utah whose back­ground could not be more dif­fer­ent than her own. Rab­bi Rich­mond, a chap­lain at the base, offers her the sup­port she needs to sort through feel­ings about her past and the cur­rent events in Europe. With the rabbi’s help, Eleanor is able to com­plete her project with the mil­i­tary, and to redi­rect her own trajectory.