“She might be crazy, or she might be the sanest person I’ve ever met.” Some cringingly obvious lines really lower the tone of this deep south melodrama (released in the US last year with the title Tuscaloosa). It’s an adaptation of Glasgow Phillips’s novel about a white kid in early-70s Alabama: a psychiatrist’s son, he falls in love with one of his dad’s patients. The director is Philip Harder, a veteran music promo maker who evokes time and place with the intoxicatingly intense colour and heightened reality of a William Eggleston photograph. But his film, though well-meaning, is disappointingly tame and soap opera-ish.

What it has got going for it is a trio of gusty, heart-on-sleeve performances. Devon Bostick is terrific as Billy, a charismatic dope-smoking drop-out who’s back home in Alabama mooching about, working as a gardener at his dad’s psychiatric hospital. One day, he spots beautiful new inpatient Virginia (Natalia Dyer), who tells him she’s not crazy and that her dad locked her up for being a nymphomaniac. Dyer’s intelligent and sensitive performance does wonders for a character who, on the page, looks like a male fantasy: a cool-girl psychiatric case, fun-loving, free-spirited and up for anything.

Marchánt Davis completes the trio as Nigel, Billy’s African American childhood friend. He joins a group of militant civil rights activists and becomes the target of racist cops, but there’s just too much going on to properly explore the dynamics of the two men’s friendship. Another subplot in flashback reveals the death in mysterious circumstances of Billy’s mother when he was a child – a storyline that seems to exist purely to fend off criticism that here we have a film about brutal racism and oppression of women told from the perspective of a privileged white man.

• Summer of ’72 is available on digital platforms from 1 February.