Oliver (Ewan MacGregor) has a terrific dog. It’s his dad’s dog really, but by the time Beginners begins, the Jack Russell has moved in with Oliver, owing to the fact that his father, Hal (Christopher Plummer), has recently died of cancer.

The dog, named Arthur (played by Cosmo), is terrific in assorted ways: he cocks his head and follows Oliver from room to room: being introduced to his new home—“This is the bathroom, this is the living room”—Arthur looks through doorways, gaining a lay of the land. He misses Oliver sorely whenever he’s left alone, barking until Oliver returns, which is always immediately, and he seems to listen when Oliver reports on what he’s learned about the Jack Russell’s background (he’s considered cute by humans and he chases tennis balls “because they’re as close to a fox as you’re going to get”). What’s more, Arthur talks. Or at least, he’s subtitled (“My personality was created by someone else”), so you can follow Oliver’s conversations with him.

Yes, such business is cloying, but Arthur carries it off, with help from Oliver, who is admirably complicated, both earnest and self-aware. A graphic designer in 2003 Los Angeles, he’s missing his father at the same time he’s trying to convince a band called the Sads to buy his latest concept—their album art should encompass “The History of Sadness,” with a foldout set of sketches displaying all manner of occasions for melancholy and depression. These drawings, by writer-director Mike Mills, that walk a line between funny and pathetic, a line that’s uneven and odd, much like the process of grief.

The film too walks a line, less convincingly. On one side, Oliver’s memories of his father are mostly enchanting (thanks to Plummer’s utterly lovely performance), while his evolving romance with an actress named Anna (Mélanie Laurent) is mostly gimmicky. They meet way too cute, for starters, at a costume party: Oliver has come as Freud and she’s dressed as Chaplin: as she lies back on a couch and they pretend to therapize, he learns she has laryngitis, and so her half of the conversation is written on a pad. Yes, she’s insightful (“Why are you at a party if you’re sad?”), and yes, he’s charmed. They spend their first night just sleeping sweetly in her fancy hotel room bed, then leave the next morning, Anna holding Arthur’s leash as they agree to meet again.

Anna has her own father issues (indicated by her anxiety whenever the phone rings in her room, as it’s always, apparently, him), and so the two lovers must sort out their conflicting conflicts, each afraid at different times of being abandoned and absorbed. Oliver’s fears are spelled out in his narration and a series of accompanying images to illustrate and offer commentary. So, Oliver narrates, in 1955, when his parents were married, “This is what pets looked like,” and “This is smoking, and “This is what it looked like when people kissed”—all shots posed and neat like the corniest version of the ‘50s, women in wasp-waist dresses and men with close-cropped hair and closed lips.

His parents stayed married for 44 years, Oliver explains, until his mother died (also of cancer, a sign of her era as much as her marriage may be). Six months later, he adds, “My father told me he was gay.” Seventy-five-year-old Hal appears in a mix of flashbacks, different clothing choices indicating Oliver’s confusion: “I always remember he was wearing a purple sweater,” he says, but Hal might have been wearing a robe, or maybe a button down shirt. The son’s versions of his dad suggest as well a series of shifting social and political contexts, how men act and how they’re expected to act.

Visibly freed from one set of social constraints once he’s out, Hal goes on to embrace another. In his son’s flashbacks, he appears at parties with a scarf around his neck, with his boyfriend Andy (Goran Visnjic), in the hospital where he flirts with his adorable male nurse. He invites his friends over to watch The Times of Harvey Milk, he campaigns for LA Pride. As Oliver continues to grapple with his changing ideas of his dad, he must also look after him as he’s dying and also confront his mixed feelings toward Andy, who “hasn’t had it easy,” Hal explains to his son, “Be nice to him.”

While he appreciates Hal’s complete commitment, his love of life, Oliver notes his own reluctance to commit (“We didn’t have to hide to have sex,” he says of his own romances). He can describe it and worry about it, but he can’t fix it, at least not right away (at his drawing board, he lays out a series of portraits of past girlfriends, with dates showing when he met them and when he lost them, as well as his short attention span.) When Hal asks him why he hasn’t married a “great” girlfriend, Oliver falls back on a residual fear: “I just don’t want to be like you and mom,” he says, as Hal’s face reflects a fast range of emotions, from sympathy to frustration to deep and abiding love. Hal knows it’s possible to love unconditionally, but his 38-year-old child still needs to sort out that recently developed social expectation.

Anna helps and doesn’t help in this endeavor, the fantasy she embodies alternately appealing and trite: “There’s always another empty room waiting for her,” he says of her career and life on the road, “They used to make her feel free, now they make her feel the opposite of free.” Hal—even in his son’s intricate memories—maintains a remarkable capacity to cut through. Having survived his own life, and Oliver’s scrutiny, he often seems possessed of wisdom. And when he doesn’t, when he articulates limits and forgives weakness or incomprehension, he’s the perfect dad, fantastic and believable too.