Takes place 35 years after the second episode.
The idea of the "aura" used by Dawn comes from the aura used by Salvor Hardin and Hober Mallow in the first book, both Foundation men. It is a critical point in the story "The Merchant Princes" that the Empire CANNOT engineer such a device, because their technology is based on an abundance of metals, so everything has to be gigantic, while the metal-poor inhabitants of Terminus had to do without much metal, and as a result, miniaturized everything, making them magicians to everyone else.
The friendship between Dawn and a gardener recalls the friendship between Hari Seldon and a gardener in the Imperial Gardens in the second prequel book ("Forward the Foundation", second part: "Cleon").