Complex sentence: Fifteen-year-old Clary Fray is partying hard at the Pandemonium Club with her best friend, Simon, when she sees a crowd of strangely behaving, but incredibly attractive teens sneak into a storeroom.
Split into simpler sentences: Fifteen-year-old Clary Fray is partying hard at the Pandemonium Club with her best friend, Simon. There, she sees a crowd of strangely behaving, but incredibly attractive teens sneak into a storeroom.