What a difference five years can make. For Paige (Rachel McAdams), it meant a new life free from her rich, controlling parents, free-spirited new friends, a loving marriage to Leo (Channing Tatum), and a promising career as a sculptor. Then she loses her memory after a car crash, and without those experiences, who is she?

In "The Vow," Paige tries to piece together her life as characters from her recent and former lives try to pull her back into their orbit. For Leo, who's both devoted and supportive of whatever path Paige needs to follow on her recovery, the situation is clear: "I've got to make my wife fall in love with me again."

For Paige, who feels freed to move in whichever direction she chooses, the way forward is less clear-cut: "I feel like I've got a do-over on my life." So will it be a return to sweater sets, law school and her conniving former fiancé (Scott Speedman) or rediscovering why she fell for the sensitive but far from successful Leo? Nicholas Sparks, meet Philip K. Dick.

The best thing in the film is McAdams, who moves through her post-amnesia scenes with a plausible mix of good humor and wariness. Her character retains our sympathy even when she's making other people's lives difficult, and you can see why Tatum's Leo clings to her for dear life. He's well cast as a burly lug who married far above his station. Despite that "nobody's home" air of his, he projects an uncomplicated decency, and you feel for him when McAdams' disapproving parents (the underutilized Sam Neill and Jessica Lange) show him no love.

Despite its gimmicky premise, "The Vow" never teeters over into burlesque. While it won't make you fall out of your chair, it is proficient Valentine's Day entertainment. Michael Sucsy (of HBO's warmly remembered "Grey Gardens") directs with a light touch. The script, loosely based on a true story, has a fair share of surprises (and several of the cleverest pickup lines in ages). Despite too many on-the-nose moments (Paige and Leo's date spot is named Café Mnemonic), the screenplay is knowing about the small domestic details that serve as glue or irritants in ongoing relationships. At breakfast with Leo, Paige gobbles a bacon strip before he can remind her that she's vegetarian. The old Paige loved being tickled; the new one hates it.

The film is aware that for two human beings to be in an emotional and sexual relationship without causing pain to each other demands constant vigilance; in real life the anything-goes spontaneity that propels romantic comedy would wear thin fast. In less skillful hands, "The Vow" would be a guilty pleasure. Instead, it's just a pleasure.