I watched this last night. Macha Meril is incredible as the instigator. She's good at crazy. I don't think the film was as brutal as Last House on the Left but I found it more disturbing overall. As mentioned before, the fact that the train passenger sees what's going on and instead of helping, joins in and then is able to go back to his normal life as if nothing happened. But also, that Meril's character is able to (seemingly) get away with everything despite her leadership role. She'll also blend back into society with none the wiser. Very solid film.