Rihanna, Freddie Highmore in 'Bates Motel'
CNN  — 

The following contains spoilers about “Bates Motel.”

There’s a fine line between creative risk-taking and sacrilege when dealing with well-known properties. While “Bates Motel” might not have committed the latter, it has seemingly sacrificed the right to bill itself as a prequel to “Psycho.”

The A&E series always appeared to come with a built-in expiration date, facing the danger of running out of real estate as it chewed through story related to Alfred Hitchcock’s 1960 horror classic. The contemporary setting also made the proceedings less spooky, what with cellphones and other modern devices that alter the dynamics of, say, being alone in the basement with a murderer dressed like his mom.

Still, the announcement of a fifth and final season that would overlap with the movie actually created some excitement: after an ill-advised remake, this offered an alternate window into the story, including how these events unfolded from the perspective of Norman/Norma Bates.

Although the producers had stated that they would be deviating from the movie in ways that will “blow the fans’ minds,” they remained understandably coy as to how. Before the season began, they told USA Today that there would be references to “Psycho” “through the lens of ‘Bates Motel.’”

The latest episode, however, didn’t just play with “Psycho” canon, but upended it, going wildly off script.

So while the audience was no doubt waiting for guest star Rihanna, as Marion Crane, to meet a grisly end in a recreation of the movie’s iconic shower scene, she unexpectedly escaped, with Norman (the brilliant Freddie Highmore) eventually finding a different victim: Sam Loomis (Austin Nichols), Marion’s lover, and the guy who wound up catching him in the movie.

“Bates” hasn’t been creatively shackled by “Psycho” through its run, which was perhaps wise as a practical matter. Staying unerringly faithful in the context of an episodic series is the sort of juggling act that tends to handcuff storytellers.

At the same time, the series was clearly sold and marketed based on its connection to the movie. And while obliterating the film’s timeline might have the initial sensation of feeling fresh and clever, it also comes across as a major cheat, as if there was a bait-and-switch aspect to the whole exercise.

That’s a shame, really, to the extent that it casts a pall over the show, since Highmore and Vera Farmiga, as Norma, have delivered splendid performances throughout. The writers have also cleverly toyed with contemporizing “Psycho,” such as Norma taking Norman’s body out for a spin to pursue hedonistic fun.

Monday’s episode seems almost sure to be polarizing. “Bates Motel’s” loyal fans might have bonded with the characters to the point where the show has assumed a life of its own, and fidelity to “Psycho” is beside the point.

Those more invested in Hitchcock’s movie, by contrast – or who at the very least would rather not see it rewritten – have good reason to feel jerked around, and less incentive to stick around for the remaining episodes.

Oh, and that fly the Norma personality said she wouldn’t hurt at the end of the movie? Here’s a bet that he’s a goner.

“Bates Motel” airs Mondays at 10 p.m. on A&E.