“Are you real or are you one of those manic pixie dream girls?” a man asks a woman he met five hours earlier. The two are in a bar downing shots: he is Bart (Finn Wittrock), a Los Angeles writer whose life is a mess, and she is Vienna (Zoë Chao) a hot, funny cool girl carrying a handbag stuffed with cash. She picks him up in a half-empty cinema and seems too good to be true.

And disappointingly, Vienna does turn out to be more fantasy girl than an actual character in this fluffy romance. Like the classic MPDG she exists mostly for the purpose of saving Bart. It’s a shame because Chao (an actor I’ve not seen before) is funny and warm, with a sharpness that gives her quirky up-for-anything character some added layers of realness.

The film begins promisingly enough, director Stephen Basilone’s script nicely setting up that something is not quite right about Vienna. She doesn’t have a mobile phone or a credit card – and she’s vague on the basic details about her life. The big reveal is that she is from the future: sent back in 2052 by a government agency to tinker with the past in ways that will benefit society. (Butterfly effect rules apply so there are limits on what she can tweak.) Of all the inherent implausibilities about this implausible storyline, the biggest is that she is carrying around thousands of dollars and cash money is still a thing in the future.

On the plus side, there’s an easy romantic chemistry between the two leads. And the ridiculously good-looking Wittrock is perfectly fine as Bart, though his sad face at the beginning is a bit one-note – fixed into the expression of a man who’s just seen his puppy thrown off a bridge on to a busy dual carriageway. But Chao is the standout here. She deserves more – a leading role of her own, at the very least, and a character with an inner life and interests of her own.

• Long Weekend is released on 12 July on digital platforms.