Vegas

S5, E19: Police find a desiccated corpse on a desert road outside Las Vegas Nevada the seventh victim of a bizarre serial killer. Detective John Sheppard called in to assist is baffled by these murders. Then a clue traces of radiation found on the bodies leads him to a strange looking man with super human attributes who easily evades capture. Some time later Sheppard is detained and driven to Area 51. There he meets Dr. Rodney McKay who reveals that the suspect is in fact an alien - a wraith - who feeds on human energy. What's more McKay and his team have traveled to Earth from the Pegasus Galaxy by way of a stargate to prevent this wraith from compromising the security of the planet. But so far Sheppard is the only one who's been able to get close to him.