Four hundred years before the Curiosity ever left dock, something else came to WR 104 asking the same question. It never left.
The away team goes into a structure the size of a world to find out what lives inside it, how long it has been there, and what it is aimed at. One of them does not come out.
The rest come home to a planet the colour of ash - and to an archive proving that three hundred and forty-one warnings reached Earth before theirs, and that every single one was read, filed and declined.
What is left of humanity is eight thousand people buried under the Moon, ninety thousand on Mars, and four thousand on a mining outpost that has only just finished fighting off pirates. What is left underneath the Earth is older, angrier, and has been waiting a very long time for somebody to come down and knock.
And in a cell that is not quite a cell, a man nobody is coming for begins to count.
The concluding book of the Curiosity duology. Book One, Curiosity: The Crossing, is available now.