About five minutes before the final credits, Jesse Moss’s award-winning documentary hits us with the narrative twist of the year: it’s a doozy of a plot point, one we kick ourselves for not twigging, one that prompts the viewer to reappraise everything that came before.

Long before this unexpected development, The Overnighters has established its credentials as beautifully crafted, multi-layered piece of storytelling, and as an important snapshot of the new Great Depression. It's impossible not to think of John Steinbeck watching men and women – though mostly the former – descend upon North Dakota, in buses and vans and busted up RVs.

They’re hoping that the oil boom in the Bakken fields in the western part of the state will give them a shot at a paycheck. They leave behind deserted, abandoned small towns. They speak like the streets are paved with gold, and about people with many felonies on their record scoring of $100,000-a-year jobs. Dirty, lucrative work borne of fracking.

The state has neither the resources nor the housing to cope with this influx. Enter Lutheran Reverend Jay Reinke, a decent chap who opens his home and his church to homeless migrant workers.

Over two years, film-maker Jesse Moss drifted in and out of the pastor's makeshift 'snorer's room' and RV stop at the Concordia Lutheran Church in the little town of Williston. But over two years, the Reverend's "overnighters" programme becomes increasingly unpopular with his parishioners; some euphemistically cite fire regulations, others simply view these interlopers as trash. A local newspaper fans the flames by searching out registered sex offenders among the thousands of nomads who receive the pastor's charity.

A compelling portrait of the very best and very worst of humanity, Moss’s riveting film asks the viewer where they’ll stand as the global economic crisis worsens: with the kindly shepherd or with the mean-spirited flock?