“Grassland” is an intimate social justice drama about the bottom level of the marijuana business, a tale told in the last of its years as a banned and not merely “controlled substance.”

A single mom struggles to make ends meet by growing, prepping and selling weed out of her rental duplex’s basement in New Jersey. An aged cop moves into the other half of the duplex. You can guess the rest.

Mia Maestro (“The Motorcycle Diaries,” TV’s “Nashville,” “The Strain”) is Sofia, an Argentine immigrant estranged from her mother (Rachel Ticotin) and on her own with young son Leo (Ravi Cabot-Conyers). She dotes on him and reads to “Prince Leonardo” from Homer’s “Odyssey.”

But even at this age, Leo is pretty much a co-conspirator. He knows what mom does and is just now awakening to the problems it could lead to for her, him and her young deliveryman and sometimes baby sitter Brandon (Quincy Isaiah, Magic Johnson on TV’s “Winning Time: The Rise of the Lakers Dynasty”).

Virtually “nobody’s buying,” in this economy. She’s had problems with mites in her plants, is behind on her rent and now the duplex owner has rented the other half of it to a grandpa (Jeff Kober of TV’s “China Beach”) and his grandson Tom (Sean Convery).

Great. Leo has a playmate.

But grandad John rolls up to the place in a police cruiser, putting Sofia in a panic. Sofia’s got to hide what she does, from the actual plants to the scent, pretend she doesn’t know Brandon and keep Leo from giving away the game to Tom. She may minimize the new risks to Brandon, who has a record and isn’t stupid, and she might think she’s allaying her little boy’s fears.

“Are we criminals? Are we getting arrested?”

It doesn’t help that John’s bitter, a cop being shown the door and a caregiver thanks to what we figure out must have happened to his daughter, Tom’s mother.

Co-writers/directors William Bermudez and Sam Friedman focus not on the nature of the crime, as it then was, but on the circumstances of those wrapped up in it. It’s 2008 and the country’s in the throes of the Bush II recession.

Montclair, New Jersey isn’t Newark. This is the lowest stakes battleground in the failed, more-cultural-than-criminal “War on Drugs.”

And this isn’t TV’s “Weeds,” a sometimes jolly, sometimes dangerous lark for a housewife to find a “career” setting up and running a big growhouse-to-street distribution system. The problems, to a one, are the The System itself — racial profiling, over-empowered police, punishments absurdly out of proportion to the crime.

The risks aren’t worth the rewards, and only the most desperate would take those odds. Brandon is smart enough to know that getting out is Job One. But few will hire someone with a criminal record. Sofia thinks she knows the risks and “can hande” this. But smart people don’t get into this “business.”

“Grasslands” maybe be pretty much wholly predictable. But the performances have heart, compassion and a testy edge when that’s called for.

And this simplest of period piece parables lays bare the inequity of “justice” as pot legalization was just beginning and the “gateway drug” theory was fading into the mists of myth.

Rating: unrated, violence, profanity, drug content

Cast: Mia Maestro, Jeff Kober, Quincy Isaiah, Ravi Cabot-Conyers, Sean Convery and Rachel Ticotin

Credits: Scripted and directed by William Bermudez and Sam Friedman. A Gravitas Ventures release on Amazon Prime.

Running time: 1:29