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

The final line of the chapter states the rose symbolizes a "sweet moral blossom" to "relieve the darkening close of a tale of human frailty and sorrow."

So this tale is a story of sin and "redemption". THe redemption comes, however, at a huge cost. This is where the "human frailty and sorrow" comes in,