I might have mentioned this earlier, but most or all the Rotterdam area locations could be reached via public transportation (i.e. Light Rail).
From Rotterdam Centraal station they could ge to Den Haag with the RET E-line light rail. Similarly, to get to the Schiedam windmills they could take the RET D-line to RET A or B-line light rail. Amsterdam is way too far away, IMHO. But this is all just speculation till the episode airs.