If well executed, with a duo of good actresses in Isabelle Huppert and Chloë Grace Moretz, Greta should be a good little psycho-thriller, but unfortunately, it is not. There are just too many illogical plot twists, from unattended lost bag on a US subway without any security problem, to navie detective who got himself killed by a maniac, the plot just does not make sense. Not even Chloë Grace Moretz's good acting can save the film.