Producers: Nick Cortese, Brian Duffield, Matthew Kaplan and Jordan Levin   Director: Brian Duffield   Screenplay: Brian Duffield   Cast: Katharine Langford, Charlie Plummer, Yvonne Orji, Hayley Law, Rob Huebel, Piper Perabo, Chelah Horsdal, Laine MacNeil, Clive Holloway and Kaitlyn Bernard   Distributor: Paramount Pictures

Grade: B+

An unusual YA novel by Aaron Starmer, published in 2016, has become a most unlikely treat thanks to Brian Duffield, a screenwriter of hitherto undistinguished achievement (“Insurgent,” “Underwater”) who not only did the adaptation but took the director’s chair for the first time.  “Spontaneous” is a very dark dramedy with horror elements about a teen romance that blossoms at a high school where students begin randomly and literally exploding in the style of Cronenberg (“Scanners”) or DePalma (“The Fury”). And remarkably, it manages to be both charming and insightful.

Things begin in fairly ordinary style, as cynical Mara (Katharine Langford) shares her woes with her best friend Tess (Hayley Law) at her side.  But the routine abruptly changes when a fellow student blows up during class, splattering blood on everybody.  (A brief description of the victim is given—a practice that continues throughout via narration or cameos, which makes them a bit more than just anonymous afterthoughts.)

Sequestered by authorities for questioning, the teens offer their observations—some snarky, others fearful—and Mara catches the attention of sheepish Dylan Hovemeyer (Charlie Plummer).  Soon she starts getting text messages from a secret admirer—and one of them involving a past president is actually pretty witty.  It’s not long before Dylan approaches her and Tess and she realizes he’s the author.  He tells her that he’s had a crush on her since freshman year but has held off saying anything for fear of rejection.  They hit it off immediately, and are quickly a couple, bantering and exchanging their deeper feelings.

Meanwhile their classmates keep popping off, as it were.  One of them even takes to dressing in PPE as a safety precaution, which proves insufficient in the end.  Naturally the government gets involved, quarantining the surviving kids for tests and experimentation with potential treatments.  In isolation Mara and Dylan grow ever closer, and after their release one might hope their relationship will continue…until the screen suddenly goes completely red.

At that point “Spontaneous” turns much more serious as the consequences of what’s happened come home, and the reality of loss sinks in.  It’s made clear that teens do not handle grief well, despite the support they receive from parents and friends.  It’s also made clear, however, that they can overcome it, and a politically-inspired capper carries a punch. 

This is a challenging twist on the teens-facing-death genre—both for the darkly satiric stance of the initial acts and the dramatic, borderline tragic, one of the third.  But both as screenwriter and director Duffield manages the tonal shifts with élan, and in Langford and Plummer he’s blessed with leads who are effortlessly engaging.  The supporting cast is excellent as well, with Law exemplary as Mara’s obligatory best friend, while Rob Huebel and Piper Perabo are equally fine as his sympathetic parents.  As Dylan’s widowed mother Chelah Horsdal has less screen time, but does have a single scene toward the close that’s extremely touching.   The youngsters who play the leads’ classmates do well too, and Yvonne Orji provides a mixture of strength and vacillation as the chief government investigator. 

The production is technically polished, with Aaron Morton’s cinematography, Chris August’s production design, Sekyiwa Wi-Afedzi and Brooke Wilcox’s costumes and Steve Edwards’ editing all top-tier.  Joseph Trapanese’s score is eclectically right=on.

The anxieties of the world’s current situation probably explain why “Spontaneous” is receiving only limited theatrical release.  It deserves better.  But in whatever format you see it, it will prove an unexpectedly sharp, smart teen comedy-drama with two exceptional lead performances.