The series tells about Juan dela Cruz, an orphan boy who was brought up in a church by a Roman Catholic parish priest named Father Cito, who guided him towards goodness and faith upon Jesus. His devotion to Christ led Juan to refer to Jesus as "bossing" (Filipino for "boss", due to Jesus being considered as the "shepherd", or "boss", and the "flock" the followers of Jesus). One day, Father Cito was killed by a thief, and Juan ends up at Lola Belen's house in Quiapo, Manila. Unknown to him, he is half-aswang, the son of Samuel Alejandro, the Haring Aswang (King Aswang) and also the prophesied Anak ng Dilim (Child of Darkness). He is fated to rule over the Aswangs and take over the human race. However, Amelia, Juan's mother, is a human and a Tagabantay (Guardian), coming from an ancient lineage of defenders using the Bakal na Krus (Iron Cross) to protect the humans from the Aswangs. By the time he grows up as an adult, Juan later joins the Kapatiran (Brotherhood), a group composed of ...