Estranged from the best friend whose brother killed her sister in a school shooting, a grieving Cora receives a message on her twelfth birthday from her friend, asking for her help with creating a time portal to prevent the tragedy.
In 1943 ten-year-old Lida is torn away from her home in the Ukraine, separated from her little sister Larissa, and sent to a slave labor camp in Germany, but when she is moved and set to making bombs she sees a way to strike back at the Nazis.