In a world where implanted neural chips allow investigators to interrogate suspects through their own memories, detectives Kim Jinyeong and Seo Jisu prefer the old-fashioned method of chasing criminals on foot. Officially, they are colleagues-turned-lovers who divorced years ago; but off the record, they continue to seek each other out after work, haunted by a tangled relationship that neither has fully let go of. Then, one chilling Christmas night, Jinyeong disappears without a word. Exactly one year later on Christmas Eve, he returns and stands before Jisu as if nothing had happened. Where has he been, and what truth hides behind the silence of that missing year...?