From audible.com:
The fifth original novel from the much-loved space western Firefly, produced with Joss Whedon as consulting editor, set between the TV series and the movie Serenity.
Deadly disease
Months after Inara leaves Serenity, Mal and the crew finally learn the reason for her sudden departure: She is dying of a terminal illness. It is Kiehl’s Myeloma, a form of cancer that’s supposedly incurable, and Inara has very little time left.
A disreputable scientist
Through their shock and despair, rumors of a cure reach the crew. Expert Esau Weng is said to have developed a means to treat Inara’s condition, but he has been disgraced and incarcerated for life on a notorious Alliance prison planet.
An infamous prison
On Atata planet, inmates are abandoned with no guards and left to survive as best they can. What’s more, terraforming the planet did not take properly, so the world is a frozen wasteland. To save Inara, the Serenity crew must infiltrate the prison....