I found this in our library's book sale room.It is clearly for a younger audience, but with the "Point" imprint, I thought it might be on par with some of the old Point Horror titles I've been reading.

Lucy and Hugh are a sister and brother who awake one night to a host of creepy sounds and find themselves in a house that isn't quite theirs.Their bedroom is the same, but the rest of the house is full of furniture they don't recognize, and there seems to be an invisible barrier preventing them from leaving their yard.When they hear and see two other children running around the house, in addition to a cruel woman who appears to be the children's aunt, Lucy and Hugh decide they have been flipped back in time in order to help the children.

Unfortunately, I guessed the twist of the ending in about chapter two, so I kept waiting for Lucy and Hugh to figure out that (view spoiler)