The guide was there and we knew that a very legal process started on that day. what we did not know is that the area was completely secured and that there were three entrances. The guide arrived 15 minutes before the tour, left a message to the clients, talked to the policemen out of the two entrances, gave the names of the clients to call her in order to pick them up. The guide was waiting in the other entrance and the clients did not show. The guide stayed there for 40 minutes waiting for them. When you book a tour, we kindly ask for a phone number in case of any urgency. The clients did not have one on that day. The reservation was paid for that day to "la sainte chapelle". The guide did all her best to reach them. We are very sorry for the inconvenience. Just so you know, if you don't have a phone, you can always ask to a parisian to make a call, it costs nothing and they really help people out. You could even ask to the policemen since the guide did it. It is a piece of advice.