The PSYCHO Protagonist?

Who becomes the protagonist of PSYCHO after Marion Crane is killed?

Robert McKee in STORY states that there's a joint protagonist of the sister (Lila Crane played by Vera Miles) and Detective Arbogast (played by Martin Balsam).

I, however, believe that the protagonist becomes... Norman Bates.

Marion's death is a shock as we'd never seen the protagonist killed in a film.  The shocking murder was all the more shocking as the leading lady was killed before our eyes.   Following that, Norman discovers what "Mother" has done and he's forced to clean up the mess.  We sympathize with Norman and even root for Marion's car to completely submerge as he covers up the crime.

As the Detective/sister team investigates and closes in on the mystery of Marion's disappearance, our sympathy is with Norman.  He's a good son with a crazy Mother doing what can to stop her while protecting her.  Look, for example, at the scene where Detective Arbogast finds Marion's signature and points it out with Norman.  Are we rooting for the Detective in that scene?  I'd say, "No."

This makes the Mother skeleton scene all the more shocking.  Lila Crane tries to warn Mrs. Bates and we see that she's been long dead.  Then Norman/Mother attacks and we add it all up.  The protagonist we'd been rooting for is, in fact, the killer -- the Pyscho.   That's TWO amazing reversals in one film.

The regrettable denouement psychiatrist exposition scene wasn't needed.   It did, however, give us that final Norman smile/skeleton shot.  A great film.  

Look also for the 2015 documentary on the impact of the Hitchcock/Truffaut interview book with the filmmakers it influenced.