"Then the spring rain fell in Bianjing, and you were the only one left in the rain" means: After you (referring to the author's late wife) left, the spring rain fell in Bianjing, and I was the only one left in the rain. Stop.

This poem comes from "Partridge Sky" written by the poet He Zhu.

"Partridge Sky"

Later the spring rain fell in Bianjing?

Only you stopped in the rain?

The phoenix tree was half dead after the clear frost

The white-headed mandarin duck flies away without its companion

This poem was written by He Zhu in memory of his deceased wife Zhao. He Zhu's wife, Mrs. Zhao, was hardworking and virtuous, and the relationship between the couple was very deep. He Zhu once wrote the poem "Asking Nei" about the scene in which Mrs. Zhao mended his winter clothes on a hot summer day. The author and his wife once lived in Suzhou (Changmen is a famous city gate in Suzhou, used to refer to Suzhou). Later, Zhao died in Suzhou, and He Zhu soon left Suzhou for business and came to Bianjing City (now Kaifeng, Henan). During the spring rain, I wrote a poem to deeply mourn and miss my deceased wife, and to express my loneliness, being alone in a foreign land, and the pain of losing my companion.