It's based on a Patricia Highsmith novel which takes place in NYC;the screenwriters have transposed the action to Paris and except for the ending ,it' s relatively faithful to the original story.
A young cop is ill-at-ease in his milieu.he is fascinated by two "bobos " (=Bourgeois Bohêmes ) who live in a luxury flat full of works of art and who have posh friends.These wealthy people have a dog ,Lisa ,that is abducted by a washout who asks for a ransom.
The young cop will pull all the stops to help these people he thinks may become his friends and introduce him into their inaccessible word.And all he does will backfire against him.
The ending is different from the book which ends with the hero's sentence "I 'd have expected more....so much more"which is heard earlier in the film.Another mistake is to have canceled the scene when the cop and his girlfriend have dinner in the desirable apartment.
But all in all,fans of Highsmith may enjoy this adaptation.