OK, this is the fourth episode of
Les Revenants I've watched, the random one at the folks' and the first three episodes in sequence; and it's getting right under my skin, now...when it finished, I realised I'd been holding my breath.
The silent little boy, "Victor" [evidently not his real name] has apparently just
murdered 
the nosy neighbour who upset his mysteriously-chosen guardian Julie, by threatening to call the cops about her 'illegal adoption' of him...
He and Julie have deeply bonded, really quickly; which is a little odd since she's a sweet dyke who is very traumatised after being savagely attacked herself, by a knife-wielding psycho, seven years before
Also, it seems to have been him standing in the road that caused the accident in which the 40 in the coach died, which started all this...and he's so cute!

"To learn who rules over you, simply find out who you are not allowed to criticize" - Voltaire