'What If' (PG-13)

The central question driving the romantic comedy What If involves the eternal mystery about men and women and whether they can just be friends. There was, however, another question the screenwriter should have asked: Why does the script focus on the wrong couple?

What If is based on a play, so maybe that query should be directed elsewhere. And the movie does have an appealing cast and moments of quirky charm — just the right amount of quirky charm, too, not too much, not too little, not always an easy balance to achieve. But heralding it as the romcom that’s going to reinvent the genre for millennials is a bit of an overstatement. Besides, that task was already accomplished by the breezy, inventive and much better (500) Days of Summer.

Daniel Radcliffe (the Harry Potter films) and Zoe Kazan (Ruby Sparks) star as Wallace and Chantry, who meet at a party in Toronto and connect instantly. Quality banter is the backbone of the romcom, and Radcliffe and Kazan go back and forth like old pros, although chatting up a woman about “poo” — and I’m quoting here — didn’t used to work this well.

Usually after such an evening, a couple would at least exchange phone numbers, poo or no poo. Chantry does give Wallace her number (on a piece of paper — how old-fashioned), but even as she’s handing it to him the words “my boyfriend” are dropping from her lips. Wallace, a med school dropout who’s still grieving over his last breakup, tosses the number away once he’s alone, sure his chances are doomed.

But Wallace and Chantry keep running into each other, and, hey, why can’t they be pals, she asks. Her boyfriend Ben (Rafe Spall) won’t mind (he does). So Wallace decides to give friendship a shot, with predictable mixed results.

The rest of the movie follows the unsurprising path of Wallace trying to hide his feelings, which gets harder once Chantry’s sister starts hitting on him. Radcliffe and Kazan work up a pleasant, unthreatening chemistry. But Wallace is a sad sack and a bit of a coward, and Chantry waffles, and we’re all too aware the walls keeping them apart are easily scaled.

And then there is Allan, Wallace’s best friend. Allan is played by the magnetic Adam Driver (HBO’s Girls), and he owns every scene he’s in. A truly unique and modern romcom wouldn’t have bothered with clean cut, dull Wallace and indecisive Chantry; it would have focused on Allan and the equally wild Nicole (Mackenzie Davis), who meet at that same party and recklessly hurl themselves at each other. They are impetuous, brash, obnoxious, playful, ridiculous and so much more interesting than Wallace and Chantry that you can’t help but wish the movie dug deeper into their passionate bond. Now that could have been a movie worth swooning over.

Cast: Daniel Radcliffe, Zoe Kazan, Adam Driver, Rafe Spall, Mackenzie Davis.

Director: Michael Dowse.

Screenwriters: Elan Mastai. Based on the play “Toothpaste & Cigarettes” by T. J. Dawe and Michael Rinaldi.

A CBS Films release. Running time: 102 minutes. Sexual content, including references throughout, partial nudity and language. Playing at: area theaters.