Farscape (1999 - 2003): Twice Shy

Chiana purchases Talikaa, an abused slave girl from a passing Trading Ship. When the crew starts acting strangely and Talikaa goes missing, they realize she may not be as innocent as she first seemed. The crew tracks down the Trading Ship only to find its occupants have succumbed to a painful death, the result of neural harvesting by an alien arachnid. When it is revealed that the arachnid is Talikaa's true form, Moya's crew must hunt down Talikaa before they suffer the same fate.