According to the last sentence, what kind of tale is The Scarlet Letter

The last sentence of The Prison Door (chapter one) is, "It may serve, let us hope, to symbolize some sweet moral blossom, that may be found along the track, or relieve the darkening close of a tale of human frailty and sorrow."

This indicates that there is a moral or lesson to this tragic story that will serve the reader despite the sorrow it contains.