Anyone who has seen a Nicholas Sparks adaptation or two (2004's "The Notebook," 2008's "Nights in Rodanthe") and think they know what they are in for with "Dear John" might just be surprised by how the story progresses and where it ends up. The surprise, however, isn't a good one, the film becoming much ado about nothing by the time the uninspired conclusion leaves the viewer shrugging from indifference. Yes, Sparks still touches upon melodramatic subject matter—deaths, war injuries, mental disabilities, terminal illnesses, just to name a few—but director Lasse Hallstrom (2005's "An Unfinished Life") and screenwriter Jamie Linden (2006's "We Are Marshall") have changed for the worse some of the key details from the book, turning a meaningful and bittersweet tale of love gained and lost into an episodic, underdeveloped, typical romance with muddily conceived plot turns.

They meet by chance along the beaches of Charleston, South Carolina, in 2001. 21-year-old John Tyree (Channing Tatum) is home on a two-week leave from the Army. Savannah Curtis (Amanda Seyfried) is on spring break from college. By the time they must go their separate ways, they are helplessly in love, reluctantly willing to part while John finishes up his tour of duty. When he tells her, "Twelve months, and then I'll be home for good," it comes as a harbinger of doom. With the tragic events of 9/11 only a season away, it becomes immediately clear that he won't be returning as soon as he thinks. At first keeping their relationship alive through the letters they agree to send to each other, John's ultimate decision to reenlist when the country is at its lowest point puts an additional strain on things. When Savannah opts not to wait for what may be several more years before John returns, it is the catalyst that significantly changes the course of both their lives.

The target audience of "Dear John"—women of all ages—will come for the love story between hot young stars Channing Tatum (2009's "Fighting") and Amanda Seyfried (2009's "Jennifer's Body"), but that in a lot of ways is the picture's weakest element. Tatum, in his most grown-up and confident performance to date, and Seyfried, given less screen time for the sole reason of keeping the viewer in the dark about a third-act revelation, share solid chemistry together, but aren't together enough to build on their initial attraction and subsequent connection. The first half-hour, wherein John and Savannah are first getting to know each other, is a promising, dreamy precursor that the rest of the film tries—and fails—to live up to. The use of 9/11 as a plot point serves its purpose, but is almost cowardly in its treatment, the characters never outwardly discussing the event, what it means to them, or the emotional impact it causes.

What does hold more weight than expected is the relationship between John and his single father (Richard Jenkins), a quiet, somewhat shut-off soul with a sprawling coin collection. When Savannah meets him, she is enamored even as she suspects he may have a mild case of autism. John grows defensive at first over the insinuation, but his realization and, finally, acceptance of his father's developmental disorder helps to once again bring them closer together. Unfortunately, John's devotion to the military keeps the two of them apart for too long and almost strips John of the chance to finally express to his father what he means to him. In a deeply touching and complex turn that raises above the usual filmic portrayal of mental disabilities, Richard Jenkins (2008's "Burn After Reading") is outstanding. Playing a character who is warm yet incapable of really showing his feelings couldn't have been easy, but Jenkins more than pulls it off. A late scene between himself and Tatum is especially powerful in the way it is acted and handled, full of truth and free of sappiness.

"Dear John" loses its grip by the last half-hour, the story dragging out and going nowhere special. An act of great generosity and sacrifice that John makes proves wildly underwhelming and anticlimactic, the outcome wrongly altered from the book and lessening its meaning. The very ending, too, is a cheat in the way it tosses out the entire point of Nicholas Sparks' novel for the singular purpose of adhering to a tired genre formula that would be right at home in a romantic comedy rather than a drama. This is especially disappointing coming from a filmmaker of Lasse Hallstrom's stature, who should have known better. Walking out of the film, John's bond with Savannah plays as an afterthought to the love story he shares with his father. That is the true heart of the movie. The rest of it, alas, crosses overly familiar terrain, drowning in a lack of ambition.