Doctor Rodney McKay can't believe his eyes when he discovers a moon leaving planetary orbit for a collision course with its own sun. Keen to investigate, he finds something astonishing on the moon's surface - an Ancient city, the mirror of Atlantis... But the city is not as abandoned as he thinks and Colonel Sheppard's team soon encounter a strange sect of Ancients living beneath the surface, a sect devoted to decadence and debauchery, for whom novelty is the only entertainment. And in the team from Atlantis they find the ultimate novelty to enliven their bloody gladiatorial games…