As checkout time approaches at A&E’s Bates Motel (series finale, Monday, 10 ET/PT), the Norman Bates saga, born as a prequel to Alfred Hitchcock’s classic film Psycho, has charted its own course.

The series has featured the Psycho basics — Norman (Freddie Highmore) as a disturbed killer who murders his mother, Norma (Vera Farmiga), and the forbidding Victorian house looming over the motel — but it separated from the film by adding its own elements, giving Norman an extended family and bringing to life Mother (again, Farmiga), the imagined character who protects and vexes Norman.

Bates swerved dramatically from Psycho in the middle of its final season, with Marion Crane (Rihanna) arriving but escaping Norman’s wrath, which she didn’t in the film, and Sam Loomis (Austin Nichols), the straying husband of Norman’s friend Madeleine (Isabelle McNally), filling in as victim in the iconic shower scene.

“It was always our intention to have those episodes be a collision between Psycho and Bates Motel, to not just redo Psycho but ultimately serve the story we were telling, which was how Norman got the way he got. Having it meld with Norman starting to understand his own pathology, how he became who he is and why he invented Mother, that it was burying this rage he had about his abusive childhood,” executive producer Kerry Ehrin says. “It was rage against his dad that Sam became a placeholder for.”

Norman’s fate is up in the air after last week’s episode. He was facing murder charges culminating from the killings of Sam and two others. Half-brother Dylan (Max Thierot) hired a lawyer and stuck by Norman, creating friction with his wife, Emma (Olivia Cooke), whose mother Norman is accused of murdering.

All was upended at the end of the episode, when former Sheriff Alex Romero (Nestor Carbonell), enraged at Norman after the loss of wife Norma, stormed the jail and took him away at gunpoint.

“What was great about the last four episodes is we were able to move past (Psycho), with the idea that anything can happen,” says Highmore, who is taking part with co-stars and producers in a half-hour commemorative special after the finale.. “It’s no longer tied to that source material.”

Norman, however mentally unbalanced, tries to justify the killings in his own mind.

“We were trying to walk this tightrope where we wanted to keep the audience sympathetic to…