The plot follows the two characters who have recently married and are going to Niagara Falls on their honeymoon. Silas Parker (Franco) is a thief who marries Camille Foster (Miller), his parole officer's niece, in hopes it will be his chance to escape to Canada. Silas cannot stand Camille and she is blind to how he really feels, believing that everything will be all right once they get to the falls. After their wedding Camille frets about there being no rice thrown and how that is bad luck.
On the way to Niagara Falls they crash their honeymoon bike and Camille dies in the accident. Thinking that he killed Camille, Silas runs away, breaking into a nearby house to call the police but hanging up before he reports the accident. When he returns to the scene of the accident he finds Camille up and washing in a nearby river. Over the course of the trip Silas realizes that Camille really did die in the accident as she starts to decay. While taking care of her, Silas shows a kinder side due to his guilt over having accidentally caused her death.
Meanwhile, the police believe that Silas actually killed his wife and begin to hunt him down. The couple have to evade capture several times and end up traveling with an old rodeo cowboy (Carradine) with colored horses. One of the horses, Maggie, is old and should have died years ago but is still sticking around for some reason. As Camille physically deteriorates she and Silas grow closer, eventually dancing and kissing in the rain. Silas says that while he never believed in anything, Camille believed in him when no one else ever had.
The couple travels with the cowboy until he has a breakdown and sets free all his horses. Seeing that the old Maggie will not leave his side even at gunpoint, the cowboy mounts the horse and they ride into the dawn.
The couple finally reach Niagara Falls and take the boat tour together. As Silas smiles down on Camille, happy to be with her, she tells him that she is ready now. He turns to ask someone to take their picture, and when he turns back she has vanished. He gets off the boat and heads towards the Canada–US border, but stops and goes back looking for Camille. He is then spotted by the police and chased to the edge of the Niagara Falls viewing point. He screams out for Camille – not believing her to be truly dead and gone – and the police, thinking he is still evading arrest, shoot him. Camille suddenly appears, riding toward him on the horse, Maggie. She asked why he did not go on without her and he said he could not. He mounts up behind her and says "I love you" for the first time. They kiss and then turn toward the falls. Camille says "I had a great honeymoon" and Silas answers "Me too."
Then Maggie gallops forward and jumps over the edge into the Niagara Falls with Camille and Silas on her back, all three disappearing into the mist. After they jump, rice starts to fall from the sky.James Franco – Silas Parker
Sienna Miller – Camille Foster
David Carradine – Cowboy Bob
Scott Glenn – Sheriff Foster
Ed Lauter – Sheriff Steiner
Mark Wilson – Deputy Ruddy
The film played at film festivals in Europe and North America throughout 2008. Camille had a domestic (US) theatrical release on November 14, 2008 - same day as Quantum of Solace - followed by an international theatrical release including Russia, Mexico, and the UAE.
Dustin Sommer of Blu-ray Review wrote "If you're in the mood for something out of the ordinary, Camille is a sure bet." Chuck Bowen of Slant Magazine rated it 2.5/5 stars and wrote, "An admirable Sienna Miller effort isn't enough to save this strange, plasti-quirky mess." Brian Orndorf of DVD Talk rated it Rent It and called it a black comedy that is "complete absurdity".
Louise Keller of Urban Cinefile wrote "A surprisingly touching black comedy with a twist, this love story starts in earnest after the bride is dead. Yes, dead. You read it correctly. But being dead is not enough reason to stop the honeymoon and it's credit to Sienna Miller and James Franco in the central roles to keep the premise credible as long as it does. The first hour in which we get an insight into the volatile relationship between Camille and Silas holds well but there's a dip in last half hour, when the film struggles before it finds its resolution. This impossible love story has plenty of charm as well as bizarre and often farcical situations. We are able to make that leap of faith mostly because the characters are grounded in reality.
When we first meet Miller's Camille, she is an air-head chatterbox blonde madly in love with her bad-boy boyfriend Silas (Franco). She is living in her own world, oblivious to the fact Silas may not feel the same way about her. For Silas, Camille is his ticket to freedom; her Uncle Raymond (Scott Glenn), who happens to be the town sheriff, has let him out of jail in order to marry his niece. This is the wedding of her dreams and for Camille, who looks lovely in her traditional white gown, nothing will stop her happiness. Next stop Niagara Falls, Camille's dream honeymoon destination and the newlyweds set off on his motorbike for the long road trip. But her non-stop harmless chatter irks Silas and there's a poignantly funny scene when they have a major confrontation in a roadside diner. That is where they meet David Carradine's colourful Cowboy Bob, who has a team of pastel-painted rodeo horses.
What happens next and the way it is revealed is crucial to the film's success and director Gregory Mackenzie directs this aspect of Nick Pustav's script with great sensitivity. 'Every marriage has its problems in the first couple of years; yours just happen to be in the first couple of hours,' Uncle Raymond had said. Never a truer word has been spoken. There's an accident, things become peculiar, yet Mackenzie cleverly keeps his characters real as Silas discovers there is something strange about his bride. Camille is oblivious to her plight. The humour turns black as Camille starts noticing her decaying body starts to smell. 'You sure are an unusual couple,' Cowboy Bob comments.
This all happens early in the film and there is a long way to go. Fortunately the film doesn't rely solely on its novelty but keeps its poetic and romantic notions alive throughout. It's a road movie, a black comedy and a romance. It's unusual alright and I like the poetic ending which arrives unexpectedly, just when you wonder how this crazy premise can possibly end."