What Grows between the Stars

What is happening in the Viridian Halo, the gigantic greenhouse in orbit around Ceres, in the asteroid belt?
If nothing is done, millions may die of starvation.
So the Empire is sending the most improbable hero to save the day: Dr leon Hoffman, Biologist and descendant of Mrira Hoffman the creator of the Viridian Halo.
With him a young woman with the bad habit of quoting long dead and forgotten authors, but extremeny accurate with her gun.
What will they find in the greenhouse? What monsters had been unleashed? And from where?