It's 1962 and physics student Grace Pulansky believes she has met the man of her dreams, Robert Jones, while serving up slices of pecan pie at the local diner. But then the FBI shows up, with their fedoras and off-the-rack business suits, and accuses him of being a bomb-planting mass-murderer.

Finding herself on the run with Jones across America's Southwest, the discoveries awaiting Gracie will undermine everything she knows about the universe. Her story will reveal how scores of lives - an identity-swapping rock star, a mourning lover in ancient China, Nazi hunters in pursuit of a terrible secret, a crazed artist in pre-revolutionary France, an astronaut struggling with a turbulent interplanetary future, and many more - are interconnected across space and time by love, grief, and quantum entanglement.