In all the universe, no species reached for the stars without “uplift” guidance, except possibly humankind. Did some cryptic patron race begin the job long ago, then abandon us? Or did we leap all by ourselves? That question burns, yet a greater mystery looms ahead, in the furnace of a star. Under the caverns of Mercury, Expedition Sundiver prepares for the most momentous voyage in our history – into the boiling inferno of the sun, seeking our destiny in the cosmic order of life.

(From Goodreads)