The 24-hour veterinary clinic acts like a bridge, witnessing the birth, separation, sickness and death of animals that human ever loved. On the contrary, also filled with our hope and despair. Some of their lives are in danger because of human’s selfishness and ruthlessness. "Once They Were Here" tells the fate from different animals on the choice of human. Perhaps it is not pure love and random. The so-called equality of life is only reflected in the uninterrupted heartbeat.