Sima Voskresenskaya, who lost her parents at the very beginning of the war, lives in an orphanage and secretly keeps our family cross, reminding her of her beloved family.

Twelve-year-old Serafima and Fyodor are trying to save the holy places of the monastery of St. Seraphim of Sarov from destruction by construction. The boys are opposed by one of the leaders of the local defense enterprise - Shmelev, who is also the cousin of the early orphaned Fyodor. Thanks to love, friendship and the power of faith, the boys manage to enlist the support of the new head of the nuclear center under construction and defend the holy places.