Clifford Pyncheon doesn't really "walk" into the House of the Seven Gables in the typical sense. He's released from prison after being wrongly imprisoned for 30 years and *returns* to the house, his ancestral home, which he inherits after the death of his cousin, Judge Pyncheon.
His return to the house is significant because:
* It represents the return of the past: The Pyncheon family's history of greed, cruelty, and injustice is embodied in the house itself. Clifford's arrival is a symbolic reawakening of this legacy.
* It highlights the themes of guilt and redemption: Clifford's imprisonment is a direct consequence of his family's sins. His return to the house, despite its dark history, provides him with an opportunity to confront his past and perhaps achieve some form of redemption.
* It sets the stage for the unfolding of the novel's plot: Clifford's arrival sets off a chain of events that will ultimately lead to the downfall of the Pyncheon family and the dismantling of their oppressive power.
It's important to note that Clifford is not simply walking into the house; he is stepping back into a world that has been shaped by his family's past and is now being reconfigured by his presence.