2121: Wading through a drowned fenland, Jean is searching for a lost village and a hillside church that appears only in dim memories of the world before it was engulfed by rising sea levels, deserts and floods. She is looking for a time capsule buried over 160 years ago, a symbol of hope for a different future.

1958: Coming of age in a drab and exhausted post-War London, Ida finds herself questioning the assumptions of her mother and her Uncle Roy. Wanting more from life, she is drawn into circles of political activism, jazz clubs, and life lived on the margins of conformist society – places where there are as many questions as there are possible answers.

Separated by decades and a planet turned upside down by climate shifts, the lives of these two women begin to draw together. As Jean closes in on the location of the time capsule and Ida prepares to take part in the first Ban the Bomb march to the nuclear weapons research centre at Aldermaston, their fates dramatically collide.