though not one word of the matter had ever passed between them , they knew that the memories the old man had of this house needed to be changed -not erased certainly , for no power on earth could erase belgarath 's memories of his wife , but rather they needed to be altered slightly so that this thatched cottage might also remind the old man of happy hours spent here , as well as that bleak and terrible day when he had returned to find that his beloved poledra had died .