Orion Tilt

Marya, a captain of an alien starship, is drafted by her husband into a special mission to Earth. She supports her home planet's quest in taking back a precious artifact which is theirs but is surprised to discover a hidden agenda of the mission when her husband releases a plague. The pathogen is an outlawed biological warfare that will annihilate mankind leaving everything else untouched. Her husband hopes to prepare the blue planet for eventual colonization by their kind, the Centaurian. 

Once she learns of his evil plans, she rebels and flees to the planet in a  hope to save the humans. She will do everything in her power to succeed, but without her starship, and all alone, what hope does she have?