There has been a good deal of snarky chatter about how Bella Thorne’s soaper “Midnight Sun” has pretty much the same plot as last year’s “Everything, Everything” with Amandla Stenberg, and it does. The question of indebtedness—or plagiarism, if you want to be nasty—is more complicated than that, though. “Sun” is based on Norihiro Koizumi’s 2006 Japanese movie, while “Everything” was adapted from a YA novel by Nicola Yoon that didn’t come out until 2015. So who’s borrowing—or pilfering—from whom?

Whatever the answer, the crime is at most one of petty larceny, because the plot—about a girl with a disease that makes contact with sunlight potentially fatal, who nonetheless ventures out of the safety of her house for love—is hardly worth stealing. Both movies are just adolescent variants of 1940s weepies like “Dark Victory,” and neither is likely to have much of an impact on anybody besides the most susceptible teenage girls.

In the screenplay fashioned by Eric Kirsten from Koisumi’s original, Katie Pine (Thorne) was diagnosed with xerodema pigmentosum after the death of her mother, a loving woman who taught her to play the guitar. Since then she has been home-schooled by her protective father Jack (Rob Riggle, playing the nice guy this time around, a bit too heavily). But for years she has watched attractive neighbor Charlie (Patrick Schwarzenegger) as he’s passed by her window, over which time he’s grown up into a strapping young high school senior.

Jack sometimes allows Katie to go out after dark to play her songs at the train station, and who should stop by one night but Charlie? Embarrassed, she runs away, but he finds her journal and eventually they connect, helped by her best friend Morgan (Quinn Shephard) despite the jealousy of his previous girlfriend (Tiera Skovbye). They grow closer over time, always going out after the sun has gone down though she continues to conceal her condition from him; one night he takes her on a train ride, where he prompts her to play her guitar on the docks, to the delight of passersby (who must be starved for entertainment).

Unhappily, a moonlit dip has thrown Katie’s watch out of commission, and before she realizes it, the sun is coming up. She dashes home, but too late, and tests indicate that being in the sunlight has taken a toll. Meanwhile Charlie, whose college swimming scholarship had been revoked because of an injury caused by his own recklessness, is encouraged by Katie to begin training again.

It would be unfair to get specific about how all this turns out, but it’s certainly appropriate to note that at least “Midnight Sun” doesn’t go the completely dishonest route of “Everything, Everything,” which contrived to have its soapy cake and eat it too. Nonetheless it’s hardly a paragon of storytelling, falling into cliché after cliché (including Morgan’s involvement with a goofy guy played by Nicholas Coombe), one of the most irritating being an overuse of musical montages. (One can say that any movie’s quality is in inverse proportion to the number of musical montages it contains. By that test “Sun” fails miserably.)

That said, both Thorne and Schwarzenegger are attractive young leads, though the movie places few real demands on them besides looking good. Riggle sets aside his usual smarmy persona to play an almost incredibly supportive dad, though he’s never quite believable in that guise; and Shephard and Coombe add some zest to their supporting turns. Karsten Gopinath’s cinematography makes it all look glossy and nice, and while editors Michelle Harrison and Tia Nolan bear some blame for those irritating montages that sometimes slow the movie to a crawl, their work at least brings it in at a decent 90 minutes.

Directed blandly by Scott Speer, “Midnight Sun” is bathetic and corny, and more suitable for a young people’s cable TV channel than the big screen. And its similarity to “Everything, Everything” certainly doesn’t help—even if the actual influence was in the reverse direction.