Star Trek: Deep Space Nine: Objective: Bajor

The Hive came from another galaxy: billions of alien beings living inside a vast, biological starship. They have already destroyed one planet, converting it into raw material and fuel for their endless voyage through the cosmos. Now the Hive is heading for Bajor and they have given the planet's inhabitants an ominous warning: evacuate in three days or die along with their world.
The Bajorans would rather die than abandon their sacred home, but their hastily assembled military fleet does not stand a chance against the awesome power of the Hive. Unless Captain Sisko can penetrate the Hive's defenses -- and discover their most closely guarded secret -- all of Bajor faces extinction.