I think he deliberately did that to unsettle her and making it about him, the poor stab victim.
Funny how Henry is always at a party as soon as anyone from the Archer family comes by, but never at any other times.
Pat does seem to have understood that he is evil but she still thought there was a chance he would allow them more time and let them go on a holiday of their choosing. When is she going to wisen up? Start recording their conversations and the preposterous things he claims. He has now uncontested claimed that Helen had a chaotic and peculiar upbringing (in court) and that Pat and Tony might abduct Henry.