What About Lila?
Psycho has some great characters in it.
Norman Bates, above all. Probably the first "modern" psychopath in movie history. He'd been preceded in Hitchcock by Uncle Charlie and Bruno Anthony, but neither of those two made quite the powerful connection with audiences. With Perkins in the role, a deep sympathy was established with Norman that he didn't really merit, but he got it anyway. And he was so damn INSCRUTABLE. What, really, went ON in that bottomless pit of a mind of his? (The TV series Bates Motel answered this question incessantly and rendered the answer boring.)
Marion Crane, too. Its funny how often Marion seems to be seen as the main character in Psycho, even though she leaves the movie less than halfway through and Norman got three sequels and a TV series. But Marion(in her underwear) gets a far bigger picture in the Psycho movie poster than Norman, and I"ve read that Janet Leigh was considered a bigger star than Anthony Perkins when Psycho came out. I've not taken a stopwatch to it, but I assume that Leigh gets more screen time in Psycho than Perkins -- she's the one on screen from hotel room to Bates Motel room; whereas Norman is often offscreen in the movies second half.
And as a character, Marion was such an empathetic character for the audience. She has sex, she steals, but we root for her, and come to care very much for her, I think.
This is my call, but I see Arbogast as the next best character in Psycho after Norman and Marion. Martin Balsam was pushed down into the "co-starring" list on the Psycho poster, but Arbogast is practically the star of his act in the movie -- co-equal with Norman, stepping in for Marion, and there to live a brief 20 minutes and die horribly and in a historic way. He also has a good supporting character's store of one-liners and character traits.
And thus we come to "Sam and Lila," the rather boring, non-romantically paired "amateur investigators" who are played by young and attractive actors but given little to do beyond expressing plot points and getting more and more anxious as more and more characters disappear.
Of the two, Sam gets to appear in the "Marion story" -- acting with Janet Leigh, shirtless and sexy and likely just having HAD sex -- so he's interesting enough in that regard. And whereas Lila barely gets to interact with Norman at all, Sam gets a nice meaty (and funny) long confrontation dialogue with him.
So...what about Lila?
What ABOUT Lila?
Lila is played by an actress who was quite pretty at the time: Vera Miles. But she is given no chance to do anything with her looks. No romantic banter(see: Eva Marie Saint in NXNW.) No deep love confessionals(see: Kim Novak in Vertigo.) No kissing scene(see: well, most Hitchcock films in general.) No unclad sexuality scenes(see: Janet Leigh in Psycho.)
No, Lila is there to appear somewhere after the halfway point in Psycho and to: piss everybody else off, bully everybody else around, refuse to engage much in the way of small talk beyond talk designed to keep everyone focused on the task at hand: finding her sister, Marion Crane.
I find this aspect of Lila pops up when, after being reasonably polite with Sheriff Chambers for awhile, just can't stand it anymore and "stops the nice talk" to get demanding of Sheriff Chambers:
Lila: THAT's what I want you to do something about!!
Sheriff Chambers: (Calmly) Like what?
But you know, it works. Chambers calls Norman right then, and Chambers reveals he drove out to the Bates Motel to investigate the very next morning.
It also works on Arbogast:
Arbogast: Well, with a little checking, I could get to believe you.
Lila: (Sharply) I don't care if you believe me or not! I just want to find Marion before she gets involved in this too deeply.
Arbogast shrugs, immediately respects Lila, does his investigating, and reports in TO Lila from the phone booth. Not to Sam. Not to Cassidy or Lowery. To Lila.
It definitely works on Sam. Lila pushes him incessantly: to drive out to the motel in the middle of the night and yell Arbogast; to go to Chambers(Sam's idea, but Lila developed it); to drive out to the Bates Motel and investigate themselves.
A nice moment that goes nowhere: Lila tells Sam that to investigate the Bates place and question Norman they will "pose as man and wife." I think Sam even glances at Lila for that idea. Its a legitimate pose, though there are no wedding rings. Can't have Norman thinking they are just a couple looking for a sex room. But there is the feeling, the MOMENT , of normalcy here. Sam and Lila COULD be man and wife. She's as pretty as Marion was; they are roughly the same age, we can imagine it, and we WANT to imagine it, given all the carnage going on.
But indeed it is just a ruse.