Teen Monster- Guardian Angel

An 8-year-old girl watches her brother get killed. She doesn't see who it is nor does she care at the moment. She is visited by an angel who says he will watch over her until she finds her brother's killer. Can Marcie figure out who killed her brother with the help of Carly and Evelyn Sanchez and everyone else that can help? And can she save everyone from Lucifer and his plan to destroy the world?