wistfully, mournfully, sadly, sorrowfully
He plaintively kicked the rock in front of him.
The old woman sighed plaintively, my husband's dead and my children have gone far away.
sadly, mournfully, sorrowfully eg at the funeral his close family were plaintively bemoaning his loss with tears rolling down their cheeks.
The sentence that you wrote above.
The adjective "plaintive" means sad, or mournful, as in a victim's plaintive cry. Other synonyms may be sorrowful or doleful.* Should not be confused with the legal noun plaintiff, which is the accuser in a civil case.
plaintive meaning expressive of suffering or woe
They are synonyms.
Synonyms
Relative and kin are synonyms.
They are synonyms.
synonyms
Are there synonyms for washable