I've said before that the drawing could easily be a copy. The scarf could have been planted later & the video could have been another child as the pic was blurry. None of it is concrete evidence. However, I'm sort of changing my mind on all that now.
I think Mark had some involvement - as in he may have been investigating in France. He mentioned giving up his career for Emily.
A big clue will be we find out what is was Ziane did in Morocco. Malik said that it dawned on him when he saw Ziane on TV. Why ? Did he recognise him or does he look like someone else? Malik said he would tell Baptiste 'who you are'(I think). Was he a criminal who is now in the Police? He also says his career is over. This is when he's in the car with Malik. Why would he feel that then ... Unless it's because Baptiste knows he's been supplying evidence. There must be a link between Charmaintaines & this case. Malik sees it as 'a calling ' almost to solve this case.
When Sieg is sitting in the car watching Ziane retrieve the evidence 'Return to Sender ' is playing on the radio. Is this another little 'placement?'
I think water will feature heavily at the end.
That's it for now. All my 'observations' and view points will undoubtedly be changing in the next 6 hours!