A recently divorced guy meets the woman of his dreams — then he meets her sneaky adult son in Cyrus, a new comedy starring Jonah Hill, left, Marisa Tomei and John C. Reilly.

Like circus plate-spinners, indie moviemaking siblings Jay and Mark Duplass keep several levels of emotions aloft at once. The writer/directors recognize that most of us are a whole lot of different people clamoring for attention from inside the same skin. Their characters are often ill-at-ease, hopeful, laughable, touching, confident and clueless all at once. Which makes their nuanced movies challenging to market and oh-so-rewarding to watch.

In the relationship comedy-drama “Cyrus,” they shake up the typical dynamics of a romantic triangle with a jolt of weird Oedipal tension and notes of genuine emotional vulnerability. John C. Reilly plays John, a sad-sack L.A. film editor seven years divorced from Jamie (Catherine Keener). She has moved on with her life, building a successful career and finding a nice guy she’s about to marry. John, not handsome or prosperous enough to beat the local competition, is on the verge of withdrawing from social life entirely.

Jamie invites John to a house party, where his attempts to chat up ladies become a strikeout marathon. Boozing the pain away, he relieves himself in the bushes beside the pool, where he meets Molly (Marisa Tomei). She teases him, they banter and he fuzzily inquires, “Are you flirting with me? That’s insane. I’m like Shrek. What are you doing in the forest with Shrek?”

Back inside he launches into a raucous sing-along to Human League’s “Don’t You Want Me” (“Best song ever!” he fist-pumps), awkwardly solo until Molly joins in on the chorus. Soon they’re making sweet music together, but she is guarded about her home life. Spying on her in near-stalkerish fashion, John discovers Molly’s secret: Cyrus (Jonah Hill), her 21-year-old live-at-home son. He’s more than normally protective of his doting mother, who home-schooled him, kisses him continually, and lets him sleep with their bedroom doors open in case he has bad dreams. Cyrus becomes John’s nightmare as he clandestinely tries to undermine his romance with Molly.

John’s dawning realization that Cyrus is sabotaging him is a wonder to behold. The light of understanding in his eyes rises like a bulb on a rheostat. So does his vexation; Molly, who has coddled the boy since birth, doesn’t register that she has created a sneaky, passive-aggressive monster hell-bent on destroying her potential happiness.

The byplay between Reilly and Hill is sublime. In their first scene together, Cyrus plays one of his keyboard-and-beatbox compositions for John. The music goes from cliched new age Yanni drivel to cliched hardcore techno in 30 seconds flat. John tries to find an appropriate expression of approval as Cyrus zaps him with laser death eyes. Their sparring becomes more painful scene by scene, and Tomei’s Molly is completely sympathetic as she tiptoes through the minefield of her new relationships with her suitor and son. She’s not thrilled to be seen as the spoils in a conflict between an adult man-child and a junior edition.

What the Duplass brothers learned in their micro-budget early features (“The Puffy Chair” and “Baghead”) are the essential skills of timing, editing and character development. In their first studio feature, they are mercifully evenhanded in their treatment of the characters. One feels sympathetic to both rivals, and as their conflict escalates one doesn’t know whether to laugh sadistically or groan in sympathy.