The uninspired title might suggest an old-fashioned backstage theatre story, but “Spotlight” is actually one of the best real-life tales of investigative journalism since “All the President’s Men.” It focuses on the 2001-2002 Boston Globe series, in the paper’s titular section, detailing the systemic cover-up of clerical child abuse that had been ongoing in the city’s Catholic diocese for many years—the opening salvo in a scandal within the wider Church that continues to the present day. Writer-director Tom McCarthy, working with his co-scripter Josh Singer, has fashioned a riveting account of the paper’s Pulitzer Prize-winning investigation, and he presents it in a spare, straightforward style that lets the sheer power of the narrative speak unencumbered by undue fuss or cinematic finery, except for superb ensemble acting and craftsmanship that serves the story unostentatiously.

That story is told from the perspective of the Spotlight staff—editor Walter “Robby” Robinson (Michael Keaton) and his reporters, volatile Michael Rezendes (Mark Ruffalo), dedicated Sacha Pfeiffer (Rachel McAdams) and detail-oriented Matt Carroll (Brian D’Arcy James)—all operating under the scrutiny of assistant managing editor Ben Bradlee, Jr. (John Slattery). It’s suggested to them by newly-appointed editor-in-chief Marty Baron (Live Schreiber), an outsider from Miami (who also happens to be Jewish in the overwhelmingly Catholic city), that they look more deeply into a recent story about a defrocked priest charged with numerous counts of molesting young boys during his years as a cleric.

The team takes up the work methodically, scouring past issues of their own newspaper for half-buried stories of alleged clerical abuse that weren’t energetically followed up, as well as diocesan registers that will reveal priests who’d been shifted from parish to parish or temporarily sidelined for unspecified reasons. Meanwhile a researcher studying pedophile priests is contacted for general information; Phil Saviano (Neal Huff), the head of a local survivors’ group, is invited to share his files with the staff; and Rezendes doggedly tries to get excitable lawyer Mitchell Garabedian (Stanley Tucci), who’s representing a group of victims, to persuade some of his clients to cooperate and help get sealed court documents made public. The indefatigable Pfeiffer will eventually secure poignant testimony from one victim, Joe Crowley (Michael Cyril Creighton), and even a startling admission from one defrocked priest, Ronald Paquin (Richard O’Rourke). And Robinson contacts a couple of bigwigs in the legal community—Eric MacLeish (Billy Crudup) and Jim Sullivan (Jamey Sheridan)—who may have helped the diocese to cover up the scandal.

Meanwhile the city and church establishment pressure the paper to tread carefully. Baron finds himself slyly courted and gently threatened by Bernard Cardinal Law (Len Cariou), while Robinson is approached by wheeler-dealer lay Catholic leader Peter Conley (Paul Guilfoyle) to consider his duty to the city and the church and the damage an expose might do to both. Nonetheless the investigation pushes on, even after a pause in the aftermath 9/11, and the first story based on it hit the stands early in 2002, with historic results.

McCarthy and Singer have weaved all these threads together skillfully, giving the overall narrative a sense of urgency without sacrificing clarity, and the cast respond with performances that add texture without going overboard. Ruffalo and Tucci are the most extroverted of the lot, the former bristling with anger as more and more evidence is collected and the latter offering a sharp-edged brand of idealism tinged with worldly wisdom. Keaton, fresh from his career-restoring turn in “Birdman,” presents a far mellower persona this time around as the veteran head of the Spotlight staff, while McAdams submerges her natural attractiveness to play a far plainer woman than usual and James likewise opts for understatement. There are more volatile turns from Guilfoyle as the oily, glad-handing Conley, Sheridan as the conflicted Sullivan, and Crudup as the silkily duplicitous MacLeish, as well as from Huff and Creighton as victims struggling to achieve long-delayed justice. But perhaps the most impressive performance of all comes from Schreiber, whose dry, understated turn as the recently-arrived editor-in-chief is a far cry from his more colorful one as Boris Spassky in “Pawn Sacrifice.”

Just as the cast avoid flamboyance, so do the craftsman. Stephen Carter’s production design is simple and stark, and the art direction (Michaela Cheyne), sets (Shane Vieau, William Cheng and John MacNeil) and costumes (Wendy Clark) follow the same pattern—as does Masanobu Takayanagi’s cinematography, which deliberately eschews the sinister gloss that Gordon Willis brought to “All the President’s Men” in favor of a more ascetic, gritty look. Howard Shore’s music is so unobtrusive that you might not even notice it.

“Spotlight” is, of course, a love letter to traditional investigative journalism—there’s plenty of nostalgia in the shots of papers rolling off presses and being plopped on porches. But it doesn’t simply glorify the Globe reporters or the paper they work for; after all, until prodded by Baron, they had blithely treated what was going on as the city as a whole did, with something very like indifference. When roused to action, however, they did their job well, in the process setting off shock waves that have had a profound effect on both state and church.