“LUCA" is based on Charles Darwin’s proposition that all species of life have descended over time from common ancestors. (LUCA stands for "last universal common ancestor.")
Oh Hyun-Jae used to be a top criminal profiler. He solved many cases with his skills, but an explosion, caused by a serial killer, ended the life of his fiancé. After the horrific incident, Oh Hyun-Jae vanished and he now lives in seclusion. Meanwhile, Cha Soo-Young is police officer in a rural area. She has a special ability, which allows her to remember everything that she saw. Due to her special ability, she is selected as a rookie detective who will partner with Oh Hyun-Jae informally.