Valhalla - Star Trek Deep Space Nine, Book 10

Tensions caused by speculation that Cardassia is about to reoccupy Bajor are complicated by the arrival of a strange alien ship. When it's discovered that the crew is dead and the ship is carrying valuable Gamma-quadrant technology, it becomes a sought after prize, which Commander Sisko must fight to keep out of Cardassian hands. Meanwhile, Sisko also finds himself at odds with Major Kira, who believes the ship is Bajoran property.
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When the alien ship suddenly seizes control of Deep Space Nine, and the Cardassians move in to try to capture it, Sisko must face off against a shipload of angry Cardassians, and the alien being controlling Deep Space Nine.