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After Zach (Aleks Holtz), a college friend of Sam's, is arrested for murdering his girlfriend, the brothers head to St. Louis, Missouri, to investigate. Zach's sister Becky (Amy Grabow) claims that he was with her at the time of the murder, although security footage places him at the scene of the crime. After a similar murder occurs, they realize that the real culprit is a being with shapeshifting abilities. The shapeshifter then captures the two, and plans to use Dean's form to kill Becky. The brothers escape and alert the police. Becky is saved, but the police believe Dean to be her attacker. As Dean later searches through the shapeshifter's lair, Sam visits Becky to make sure that she knows what they are dealing with. However, she reveals herself to be the shapeshifter and knocks Sam unconscious before morphing back into Dean. After the real Dean finds the real Becky tied up in the lair, he confronts the shapeshifter and shoots it dead—still in his form.