SPOILER ALERT — If you haven’t watched and plan to, stay away.

Although I haven’t exactly been bashful in deriding this last season of “Big Love,” hope sprang eternal that the writers might find a way to redeem themselves in the 65-minute finale, which aired March 20.

BiglovealvyAlas, no such luck. Instead, the last chapter only reinforced the impression that series co-creators Mark V. Olsen and Will Scheffer had written themselves into a corner and weren’t clear on how to wrap up all the loose ends, thus falling back on one of the most banal resolutions they could muster — literally closing the story with a bullet.

Of course, the penultimate episode didn’t make matters any easier, turning into a shootout between Bill (Bill Paxton) and Alby (Matt Ross) that felt more than a little anticlimactic — and uncharacteristic of Alby, dispatching that character (who had been one of the show’s consistent highlights) too neatly.

Still, the centerpiece has remained the relationship between Bill — the polygamist adhering to “the principle” — and his three wives: Barb (Jeanne Tripplehorn), Nikki (Chloe Sevigny) and Margene (Ginnifer Goodwin). Yet Bill’s decision to go public and announce to the world his belief in plural marriage took the show’s metaphorical aspects — to gay marriage, in particular — and bogged them down in arbitrary-seeming crises and tedious political intrigue. Throw in a belated statutory rape charge against Bill and the series appeared to be slipping farther away from its intriguing roots as it flailed wildly for subplots.

The finale did create some strong moments for Sevigny as the prickly Nikki, who admits that she lacks people skills and the milk of human kindness. Still, after the lengthy build-up — especially regarding Barb belatedly questioning her faith and relationship with Bill — to pull the rug out on that plot the way they did, through the intervention of a peripheral character, felt not only like a slap but a considerable copout. And the show’s ruminations on religion, frankly, only seemed to get more muddled and less instructive as the series dragged on.

BiglovebarbAll that’s a shame. Because at one point, “Big Love” was one of those delightful surprises — a program that at first blush looked as if it was built on a big, trashy concept, but then unearthed no shortage of fascinating characters, especially among its senior class, with Harry Dean Stanton as the prophet Roman Grant, Mary Kay Place as one of his wives and Bruce Dern and Grace Zabriskie as Bill’s squabbling parents.

The last season hasn’t entirely eradicated that goodwill, but it has left a sour aftertaste — one that makes “Big Love’s” final visit to the great beyond and a date with Heavenly Father as welcome as it was creatively disappointing.