A few more thoughts.
Tony wasn't exactly truthful when he told Emily what happened with Ian. I believe that he described it as an accident and suggested that he and Ian got into a fight in the course of which Ian was killed. In fact, as we know, it was far more one-sided, Ian did not really fight back and although Tony was acting in the heat of the moment he certainly intended to seriously injure Ian.
It made me wonder whether when we saw Ollie's disappearance we were seeing Tony's "version" of it. The account that he has given Emily and the police that may not be completely accurate.
Emily is a rubbish liar! Was anything more suspicious than the agonisingly long pause before, with Tony glaring at her, she confirmed his alibi for the evening Ian disappeared. It even made Julien smile it was so obviously false.
Poor Mark must already be in love with Emily though as he swallowed it completely.
I thought the scene where Emily and Tony left Hotel L'Eden with the press banging on the car, shouting at them and asking how they could leave when Ollie hasn't been found and with Emily seeing visions of her son was unbearably poignant.
Why didn't Tony, Baptiste and Emily try and get more information from Karl? He said that the man wore a mask, but what about finding out height, skin colour, accent? They don't even ask if he saw Ollie and if he did whether he was dead or alive.
Tony and Emily didn't seem to really react to the fact that Karl had to clean up blood, which I was shocked by, as it's the first evidence that Ollie could be injured or dead.