The newest novella from Reynolds (Revelation Space) has a simple premise: return to the past to save the future of humanity. The mission's objective involves the retrieval of genetically modified seeds, those strong enough to grow on Earth in 2080. The complication, as always, involves the effect of time travel on an ever-changing time line. Retired schoolteacher Valentina is the first to connect successfully with a future host named Tatiana through the use of a molecular-level consciousness paradox that Valentina's mother invented. This connection between past and present host are part of her mother's discovery of the relationship within a Luba pair, all of which is well explained as the adventure unfolds. Valentina's time travel produces unexpected complications that both hinder and help the mission, causing her to withhold some findings from the team. During subsequent consciousness transfers, she's forced to ask whether the motives of her fellow scientists and the AI brothers who assist the project are still aligned with the goal of preserving humanity.