Factual error: In several different episodes characters are escaping on foot to Canada, as evidenced by Ontario license plates. But the show is set in New England, and the only way to get to Ontario through the Eastern United States is by crossing a major body of water: The St. Lawrence River, Lake Ontario, The Niagara River, or Lake Erie. You can't walk there.
Continuity mistake: In some scenes it's Winter and then the next scene there are leaves on all the trees and flowers in flower pots.
