Dr. Yun, an elder ornithologist in North Korea, lost his eldest son in the war and lives with his grandchildren. Myeong-oh, the second son of Dr. Yoon, showed an unusual interest in birds from an early age. One day, he went to South Korea to observe black starlings, but he could not return and became a separated family. Yoon Myeong-oh, who became a famous ornithologist in South Korea, thinks that the North Korean ibis, which disappeared from South Korea during the study, marks it on the bird's ankle and sends it to North Korea, and asks a Japanese scholar for help. One day, while observing a black starling, his father, Dr. Yun, sees a dog tag on a bird's ankle and learns that it was put on by his son in South Korea.