Toward the end of chapter XXI of The Scarlet Letter, which is titled "New England Holiday", Hester learns from a mariner (sailor) that all her plans have been ruined. It all goes back to Hester's meeting with Dimmesdale in the forest, where they decide (at her beckoning) that they go away from the village and back to England, or anywhere else in the world but Boston.
Hester had entreated Dimmesdale to give up the falsehood that he was living under, pretending to be a pious man while suffering from the guilt of having done the things he did with Hester.
It is this falsehood that keeps him suffering, both internally and externally, over the adulterous sins that he committed with Hester, and it is this guilt that has kept him ill for such a long time. Hester convinces Dimmesdale (or so we think) that he has a better chance to lead a much better life if he moves away from it all and starts over with Hester and Pearl. As such, Hester offers to prepare everything for this departure. She even goes to the sailors herself, which is something no Puritan goodwife would have done, and plans for three spots on the vessel that would eventually take them all away.
As she is finishing the plans, the sailor tells her the bad news:
No fear of scurvy or ship-fever, this voyage! What with the ship’s surgeon and this other doctor, our only danger will be from drug or pill; more by token, as there is a lot of apothecary’s stuff aboard, which I traded for with a Spanish vessel.”
Even though he is giving her the good news of the boat is relatively disease-free, he also explains that the reason for it is because there will be a physician on board. While Hester does not understand at first, she then gets the answer that breaks her heart:
Why, know you not,” cried the shipmaster, “that this physician here—Chillingworth, he calls himself—is minded to try my cabin-fare with you? Ay, ay, you must have known it; for he tells me he is of your party, and a close friend to the gentleman you spoke of,—he that is in peril from these sour old Puritan rulers!”
Therefore, the news are that Chillingworth discovered Hester's plans and decides to book himself into that same vessel to chase after Dimmesdale and the two females. It is all part of Chillingworth's vow to make Dimmesdale's life miserable. It actually shocks Hester more than anything else, bringing down all the good spirits that she felt when she was planning it all in the forest.