“Under the Banner of Heaven” could easily be a chaotic mess. The star-studded FX miniseries has a large cast, a story that deals with tough moral issues and a lot of disparate plotlines — but it deftly crafts all of its moving parts into a riveting and thoughtful true-crime drama. 

Now streaming on Hulu (even though it hails from FX) and based on the nonfiction book by Jon Krakauer (“Into The Wild,”) “Under the Banner of Heaven” is set in 1984 Utah and follows Mormon family man Detective Jeb Pyre (Andrew Garfield) as he investigates the murder of Brenda Wright Lafferty (Daisy Edgar-Jones, “Normal People”) and her baby daughter. The grisly crime shakes up the pious small-town community where most of the cops haven’t even seen a dead body.

Spoiler alert: the culprits are Brenda’s brothers-in-law, Ron (Sam Worthington, “Avatar”) and Dan Lafferty (Wyatt Russell), who murdered her for “God told me to do it” reasons. The Laffertys, as the show explains, were big fish in this small pond, like a Utah version of the Kennedys.

Jeb and his partner, Bill Taba (Gil Birmingham, “Yellowstone”) – a Native American from Las Vegas who’s an outsider in this community – are a fictional invention for the show, and they’re one of several smart decisions that “Under the Banner of Heaven” makes.

By making Bill an outsider, the writers are able to explain some aspects of Mormons and their culture that are unfamiliar to viewers. And, since Jeb is a man of faith, they’re also able to view the Mormon church not from a place of gawking, but of sensitivity, as Jeb is forced to examine his own community.

This gives Garfield a chance to deliver lines like, “What if it’s not some outside evil … that found its way here? What if tonight is just the first edge of a bone that’s finally working its way out of our own desert’s floor?” That might feel ponderous in a less skilled actor’s mouth, but Garfield makes it land.

Another great choice the show makes is that we don’t see see the slain bodies of the young mother and her infant daughter which a lesser series would feature for shock value. “Under the Banner of Heaven” focuses on Jeb’s face as he reacts to the crime scene by dropping his professional cop façade and dissolving into tears — which conveys the horror far better than would a macabre image.

As Jeb and Bill interrogate Brenda’s widower, Allen (Billy Howle), Brenda’s story unfolds in flashbacks that reveal how, as the ambitious girl meets Allen’s family, her brothers-in-law progress from friendliness to hostility. (Russell in particular is excellent at delivering an affable façade with something that feels…off lurking beneath the surface; he’s all warm smiles paired with cold eyes and an underlying unsettling fervor that brings to mind Tom Cruise’s energy in the infamous couch-jumping incident).  

As Allen explains to the cops, even though Brenda was also Mormon, she didn’t come from the same fundamentalist branch that taught women to be as obedient and subservient to men as the Lafferty family expected, which angered Ron and Dan.  

In addition to Jeb’s murder investigation, and the flashbacks to Brenda’s ill-fated history with the Lafferty family, the show also has a third narrative thread, following the history of the Mormon church with its founder, Joseph Smith (Andrew Burnap) and his wife, Emma (Tyner Rushing) in the 1820s. These scenes aren’t bad, but it feels like the show is trying too hard to point to the roots of Brenda’s tragic story and reveal how the rot goes all the way down. The show does a good enough job of making this clear on its own.

As a whole, “Under the Banner of Heaven” is a nuanced story and an unusually thoughtful true-crime drama anchored by stellar performances.