In William Shakespeare's Julius Caesar, Cassius tells Brutus,
"The fault, dear Brutus, is not in our stars,
But in ourselves, that we are underlings."
This astute observation of Brutus holds true for Hester Prynne and Arthur Dimmesdale, as well. While it was out of Hester's control that her husband abandoned her, and while it is chance that she and Dimmesdale possess the passionate natures that they do, it has certainly been their choice to fall in love and consummate this love. So, since they are responsible for their own predicaments, it does not follow that Fate makes them victims.
Nevertheless, Hester and Dimmesdale do fall victims. But, it is not to Fate; rather, they are the victims of the cruel doctrine of Puritanism, a doctrine which does not permit sin. Since Hester's sin can never be forgiven, she lives in ignominy with the scarlet letter marking her as an adultress; in addition, she suffers great anguish from having kept secret from Dimmesdale that Chillingworth is her husband. And, with his secret sin whose ignominy he hides in his heart, Arthur Dimmesdale suffers both great psychological and spiritual anguish. This anguish that Hester and Dimmesdale experience because of the Puritanical law is what drives them to attempt escape in the hope of finding themselves and resolving their conflicts.
So, when Hester books passage for herself, Pearl, and Dimmesdale in the later chapters, she essays for them to escape their alienated life in the Puritan community by returning to England with the father of her child, hoping to reclaim happiness. However, as Chance would have it, in Chapter XXI Hester learns the devastating news that Roger Chillingworth has booked passage on the ship on which they have hoped to escape. Thus, their fates, so to speak, are sealed. Still, they are in this position because of the paths which they have taken much, much earlier in the narrative.