You're as bad as my husband, he kept saying "We've missed an episode". Right, the way I understand it is.............Peter put himself on that machine at the end of the last series, this was supposed to heal the fracture between the two worlds. I think what has happened is the fracture has healed but the cost of this was the non existence of Peter, as in he never was, so they are all going about their lives without ever have knowing him. Walter is obviously getting some kind of bleed over so I don't think that is the end of Peter (well I hope not, he's a wonderful bit of eye candy) and anyways he was seen on the set whilst filming was going on. Did any of that make sense, I'm not so sure I've got it right, I wish they had repeated the last episode of the last series to remind us of what happened. Great series though.