The series follows the story of a detective who investigates a case that leads him to a world divided into two parallel universes. Moving back and forth between the two worlds, he finds out that his love may be gone in one world, but she’s very much alive in the other. While tracking down the truth behind his love’s death, he simultaneously tries to protect her in the other, uncovering the connection between the two universes. British adaptation of the 2020 South Korean series.