Poirot had conferred with Japp in a low tone on the way up, and it was the latter functionary who requested that the household, with the exception of the servants, should be assembled together in the drawing-room. 
Japp asked that the household be assembled in the joining room.
Pundits have reasoned an implication that Wolf must be embarrassing because of Gore secretly employing her, funneling her payments and conspiring to conceal her from the press.