Message to movie-theater ushers: Get the mops out. Not because some jerk in the back row spilled his jumbo Coke, but because about a million people are going to start gushing in the middle of the teenage romance The Fault in Our Stars, and they're not going to stop until everyone is ankle-deep in tears.

A sweet and bittersweet, smart and smarting tale of cancer-stricken lovebirds, The Fault in Our Stars has Shailene Woodley as Hazel Grace Lancaster, a 17-year-old who has lived with chemotherapy, oxygen tanks, and experimental drug treatments since age 13. Her parents (Laura Dern and Sam Trammell) are brave and supportive, and encourage Hazel to bravely attend a cancer-support group at the local church. It's presided over by a guitar-strumming born again-er played by comedian and storyteller Mike Birbiglia - an early clue from director Josh Boone and writers Scott Neustadter and Michael H. Weber (The Spectacular Now, (500) Days of Summer) that they're going to approach John Green's young-adult megaseller with as much humor as possible.

Sitting there in the Circle of Trust is another cancer kid: Augustus "Gus" Waters (Ansel Elgort), who has a prosthetic leg, and eyes lasered in on Hazel. The guy is blasting her with ray guns of ardor, and it's kind of hard for her to look away.

But what's the point of falling in love when your days are numbered, and the end means impossible hurt for those left behind?

That's one of the questions at the heart of The Fault in Our Stars. And it is answered this way: Love wins out, especially when the guy who loves you confesses as much at the most perfect of moments, in the most perfect of ways, or sends you texts that make you laugh (they pop up on-screen like comic-book thought bubbles), and reads your favorite novel simply because it is your favorite novel.

That book, the one Hazel cherishes, is called An Imperial Affliction - a fictive work that functions as a giant McGuffin in the movie. It, too, is about a girl with cancer, and it ends in a dark chasm of uncertainty. Hazel needs to know what happens to the protagonist, and she writes the author, who lives in Amsterdam, to find out.

She receives a response - and an invitation to visit. Despite her doctors' cautions, she does, traveling with Gus, and with Hazel's mom, a walking emoticon of cheerful, chaperone-y laissez faire. The meeting with the scribe, Peter Van Houten (a bearded, bespectacled Willem Dafoe), goes surprisingly badly, but his assistant tries to make amends, taking Hazel and Gus on a tour of the Anne Frank house. The Holocaust hideaway diarist's famous words, "Where there's hope, there's life," echo down the stairs - stairs that the breath-starved Hazel has difficulty negotiating.

Woodley, who has come a long way since her promising debut as George Clooney's troubled daughter in The Descendants, balances grace with gravity, wit with heart. Even her sappier voice-overs ("I fell in love with him the way you fall asleep - slowly, then all at once") have the ring of truth. And Elgort (the son of photographer Arthur Elgort) is like a baby-faced Brando - disarming, and armed with a killer grin. When the pair, dressed for a fancy repast of risotto and Dom Pérignon, gaze across the table at each other, their characters' love, defiant and resolute, feels real.

Spinning in Hazel and Gus' orbit, the other characters aren't quite as convincing. Dafoe's bitter, booze-for-breakfast author is instantly unlikable, and his redheaded Netherlander assistant (Lotte Verbeek) just as instantly angelic. As the parentals, Dern and Trammell deflect grief and angst with sitcom-ish pluck. Only Nat Wolff as Gus' best friend, Isaac - who has lost one eye to cancer, and is in danger of losing his sight altogether - manages to steer clear of contrivance. Maybe it's generational: In a movie about teens, it's the teens who should rule.

And they do. With certainty. With laughter. And with tears - buckets and buckets.

The Fault in Our Stars *** (Out of four stars)

Directed by Josh Boone. With Shailene Woodley, Ansel Elgort, Nat Wolff, Laura Dern, Willem Dafoe. Distributed by Twentieth Century Fox.

Running time: 2 hours, 5 mins.

Parent's guide: PG-13 (sex, profanity, adult themes).

Playing at: area theaters.EndText