The last chapter of The House of the Seven Gables is weirdly...happy. First off, the whole public now knows that Judge Jaffrey Pyncheon is dead, and no one blames Hepzibah or Clifford. Indeed, they start to piece together the truth of how Pyncheon framed Clifford for murder all those years before. The narrator claims that, "Death is so genuine a fact that it excludes falsehood" (21.3). In other words, now that Judge Pyncheon is dead, the truth of his character starts to come out naturally. But this idea seems completely at odds with the whole rest of the book – after all, history still doesn't record whether or not Matthew Maule really was a wizard, or the facts of Alice Pyncheon's fate. There are lots of things that history seems to miss, even once the people involved have died. So where's this coming from?
Secondly, Mr. Holgrave suddenly wants to settle down happily with Phoebe. All of his political convictions seem to get swept away as soon as he admits he loves Phoebe and starts to relocate to Judge Pyncheon's old summer home. Even Phoebe is amazed at how quickly Mr. Holgrave wants to build a house in stone for future generations. Not only does this seem to be an about-face for Mr. Holgrave personally, but the whole progress of the narrative seems to show that having a family home just weighs down your kids with unpleasant expectations. Whatever happened to Clifford's conclusion that "What we call real estate [...] is the broad foundation on which nearly all the guilt of this world rests" (17.34)?
Thirdly, the narrator goes into this whole (and entirely believable) sidebar about how Clifford will never recover from his long imprisonment, even though everyone now knows that he is innocent. The narrator comments, "After such wrong as he had suffered, there is no reparation" (21.9). Yet, despite the fact that Clifford is never going to get better and it might be best for him to "pass on," he suddenly seems rather lively and chipper, all things considered. He's not a wreck of a man anymore – he's just elderly and a little disappointed.
Finally, there is the matter of Matthew Maule's curse on the Pyncheon family. In the second-to-last chapter, Mr. Holgrave deduces that the Pyncheon family has a genetic disposition toward strokes. That's how he knows that Colonel Pyncheon, Uncle Jaffrey Pyncheon, and Judge Jaffrey Pyncheon all died of natural causes, even if it was sudden and a little bloody. In fact, Mr. Holgrave goes so far as to conclude: "Old Maule's prophecy was probably founded on a knowledge of this physical predisposition in the Pyncheon race" (20.21). What a letdown! All this business about evil fate and so on just seems to have been a genetic condition handed down the Pyncheon line. We've got so many ghosts and bad omens in this story that it seems bizarre to end the tale of the curse with such a rational ending.
Mr. Holgrave even leaves the nature of his own ancestry up in the air. Yes, he is a descendant of Matthew Maule, but all he can say is that he is "probably as much a wizard as ever [Matthew Maule] was" (21.22). Does that mean Mr. Holgrave does think of Matthew Maule as a wizard or that he doesn't? The greatest magic Mr. Holgrave can draw out of his family history in the last chapter is the secret of the disappearing deed to Maine: it was in a hidden cavity in the wall all this time. Yet the hidden deed in the wall seems so mundane after we've read the legend of Gervayse Pyncheon sacrificing his only daughter to the hypnosis of Matthew Maule II just to find this deed again.
Hawthorne has done a lot of playing with gloomy houses, tainted wells, ghostly Pyncheons, hypnotized girls, and demonic cats over the course of The House of the Seven Gables. But he still ties up everything in a relatively neat, believable bow by the end of Chapter 21. His characters do manage to escape the dark past that has haunted their families for so long, no matter how impossible that seems at the start of the novel.
While haters might say that Hawthorne's decision to end The House of the Seven Gables on an up note is out of keeping with the rest of the book, Hawthorne himself really liked it. When he compared The House of the Seven Gables to his much grimmer novel The Scarlet Letter, he wrote that The House of the Seven Gables is "a more natural and healthy product of my mind" (source).