But about three o'clock a ferocious and prolonged hooting outside drove us to the window, to see Poirot alighting from a car, accompanied by Japp and Summerhaye. 
Jones also got out of the car. 
mnli hypothesis: Jones also got out of the car.  premise: But about three o'clock a ferocious and prolonged hooting outside drove us to the window, to see Poirot alighting from a car, accompanied by Japp and Summerhaye. 