Isolation is a perennial topic in Nathaniel Hawthorne's The Scarlet Letter. It comes in both internal and external forms, and it happens to all four of the most important characters: Dimmesdale, Hester, Chillingworth, and Pearl.
Hester enters the village alone; from what the reader can extrapolate, it was the loneliness that she has experienced her entire life what leads her to start an affair with the pastor of the settlement, Dimmesdale. Equally, Dimmesdale's unique upbringing, intelligence, and evident sophistication sets him quite apart from the rest of the villagers. In an attempt to have a life worth living in a place so unlike him, Dimmesdale uses his talent to effectively lead the flock, while also leading a double-life as Hester's (former) lover. His open lie, only known to him and Hester, further isolates him in guilt and self-deprecation. In the end, he even tells Hester that there is no hope for them; he shall die and enter eternity all on his own, and without Hester. With this act, the spiritual fate of Hester and Dimmesdale is forever sealed in eternal isolation.
Chillingworth's story, as he tells it himself, is that of an intellectual, older scholar whose love for knowledge isolated him from society to the point of not quite realizing the extent to which having asked for Hester's hand in marriage (while back in England), was actually quite a bizarre thing to do. Chillingworth's presumed death on his way to Boston is the stepping stone that leads Hester to love Dimmesdale and hence what leads her to ignonimity and disrepute.
As a result of Hester's actions, and of her sad notoriety as a result of Pearl's birth, Chillingworth enters the settlement in anonimity, living on his own, with revenge as his only goal. Interestingly, the isolation in the lives of Dimmesdale and Chillingworth brings them together in an unlikely relationship, where Chillingworth acts like Dimmesdale's physician. Still, even though the men eventually move in together, they still do not open up to each other; they co-exist, alone, together. In the end, after Dimmesdale's death, came Chillingworth's own, shortly after. Without anyone in the world, Chillingworth leaves his earthly possessions to Pearl; the product of the indiscretion of Hester and Dimmesdale.
Finally, Pearl is the only winner out of the sad story of Hester and Dimmesdale. As a product of her mother's "sin", Pearl is forced to live with her mother in an isolated part of the settlement. However, Pearl does not seem to mind; she actually feeds off her mother's unique attentions, fearing having to share her with Dimmesdale at any point. As an illegitimate child, she is considered a demon-child who had run the risk of being separated from Hester had it not been for Dimmesdale's subtle intervention. However, the supernatural atmosphere that surrounds Pearl dissipates as if by magic when Arthur Dimmesdale finally recognizes his sin and publicly recognizes Pearl as his daughter. When Dimmesdale dies seconds after, he literally breaks the spell of isolation that has doomed the lives of all the characters of the novel. Pearl marries, has children, and seems to have completed the circle that was begun in sadness and isolation. This circle, however, ends happily and with hopes for a better future.