Kwon Do-hun is an expert sniper and a secret agent working for the National Intelligence Service. To conceal his true identity, he lives a double life as a regular trading company employee, keeping even his wife Kang Yu-ra in the dark. Though he is occupied with his work, Do-hun cherishes his wife deeply. Meanwhile, Yu-ra, a dedicated homemaker, harbors a secret. Their tranquil existence is thrown into turmoil when Jo Tae-gu emerges, posing a threat to their carefully crafted façade.
