The brothers investigated the deaths of men who seemingly died of fear. A victim was a 44-year-old man who had a heart attack. One problem. The autopsy revealed his heart was healthy. All roads led to a ghost sickness, and guess which lucky Winchester got infected? Dean. As a result, Sam took charge of the case of the week, while his brother got scared of pretty much everything under the sun. At the end of "Yellow Fever," we were treated to an impromptu karaoke-style performance that just about stole the show.
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