The book tells the story of Hannah, a fusion scientist, who is working alone at a remote cottage off the coast of Scotland when she sees a figure making his way from the sea. It is a visitor from the future, a young man from a human settlement on Mars, traveling backwards through time to try to make a crucial intervention in the fate of our dying planet, and he needs Hannah's help.
Joe’s third book has been described as “smart, engrossing, devastating, and brought to an impeccable finish” and “a satisfying work of climate fiction involving interplanetary time travel...and the conclusion packs an emotional wallop”.