An island blows up, and from its remains a black poison fills the ocean. A team of underwater specialists with high-tech gear have to stop the poison before it contaminates the earth, but things get increasingly bizarre the more they investigate.

Abraham's wife dies in a hospital after giving birth to a son, Ariel. Abraham (Abe) is the head of a household. Biring, a housemaid, gave birth to a girl (Theresa) shortly after a few months. Theresa and Ariel grew up together. One day, Theresa's parents left for the province due to illness in the family. Theresa's parents shortly die from a passenger bus accident. Chayong, Abe's sister, sent Theresa away with her Aunt. Theresa grew up with her Aunt. Her Aunt is a prostitute and has financial difficulty. When Theresa turned 18, her aunt wants her to work as a prostitute as well to help with the finances. This prompted Theresa to run away and ended back in Manila where she was re-united with Ariel and his family.

ER explores the inner workings of an urban teaching hospital and the critical issues faced by the dedicated physicians and staff of its overburdened emergency room.