The book opens at the Swan Inn along the Thames. Joe and Margot own the inn. The inn is buzzing when an unfamiliar man straggles in injured and carrying something. He falls over unconscious. They realize that what he's carrying is a girl, who is appears to be dead. She smells like the river.
They fetch the doctor, Rita. The girl, looks to be around 4, doesn't have injuries and it doesn't look like she was in the water very long, so Rita doesn't know what killed her. The people postulate what happened to the man and someone suggests "Quietly" did it, the ferryman.
Suddenly, the girl comes back alive, though she is sullen and doesn't talk. The story of the girl starts to spread around the village.
Bess and Robert Armstrong are farmers. Robert's pig Maud was stolen a while ago. They get a torn up letter from their wayward son Robin who is always asking them for money. It mentions something about Alice, who they think is his daughter. He goes to look for Robin. He finds out his son married but tracks down the wife to find out she is dead. A local boy, Ben helps to investigate but no one know what became of Alice. Robert tells Ben to come to his farm if he ever wants work. Robert then hears about the identified girl at Swan Inn and goes to see her.
Lilly White is a housekeeper and lives at Marsh cottage and her younger sister Ann once drowned. Lilly feels guilt over what happened. Lilly hears about the Swan Inn girl, and goes to see her. She believes it to be Ann, but everyone else thinks the ages don't make sense, as Lilly is 40, how could this be her sister?
A vagrant hears and heads to Brandy Island where the Vaughans are. Anthony and his wife, Helena had a daughter, Amelia, go missing to years ago and Helena is struggling to cope, and refuses to accept that she's dead. His gardener tells him about the Swan Inn girl. When he gets there, he's sure it's his daughter.
The injured man, Henry Daunt, wakes up. He is a photographer He says the girl is not his daughter. Robin Armstrong shows up at Swan Inn too. He doesn't think it's Alice, who he hasn't seen in a year since his wife left him for another. They all agree it must be Amelia, the missing Vaughan girl. The Vaughans take her with them.
Henry says he just found the girl in the river and somehow got to safety. They tell Henry it must have been Quietly. Quietly was a man who once lost his daughter in the river. One day he comes back home with the girl, but his wife realizes he can never go back home, and now he is the eternal ferryman. He ferries people safely to shore, though sometimes if you are unlucky he does not.
Lilly still believes the girl is her sister and that she is simply living with the Vaughans and will be well taken care of. The parson kindly tries to reason will her and pays her her wages. He keeps some of it for safekeeping. Later her brother Vic comes and takes some of her money, which he often does. She had no idea what he does with it. He's an asshole.
Rita and Helena become friends as Rita checks up on the girl. She still doesn't speak. Helena is convinced the girl didn't die, they were just mistaken, though Rita realizes scientifically she should have been dead because her heartrate was too slow. Anthony is less sure it's their daughter. On her way home, Rita is robbed by an unknown assailant.
Robert goes to Bampton to look for his son. He finds out Robin has been using a fake name, "Mr. Fisher" and he hangs at at the Green Dragon, a place shady deals tend to happen. It also seems like Robin lied about Alice's mom leaving him. Robin tells him its none of his business.
Robert originally bought the farm from Bessie's dad. She was attacked and ended up pregnant, but Robert married her and raised Robin as his own with her.
Rita goes to see Henry and they run an experiment on heart rates because the girl's had been so slow. They find that being submerged cold water only makes your heart rate rise. When Helena asks Henry to take some photos of the girl, she tells them the story of Amelia's kidnapping. The nanny Ruby had gone out for a walk and when she returned the child was gone.
Six months have passed. Helena is happy. The fair is in town. Anthony visits a fortune teller, who reveals himself to be a man who says he knows the girl is not Amelia and threatens to tell his wife. Robin show up at the fair with his late wife's landlord (Eavis, the girl lived on her property so she knows what she looks like) and has come to claim the girl who Mrs. Eavis says is Alice. They take her with them and the Vaughans are left stunned.
The boatmender is skeptical and doesn't think it can be Alice Armstrong -- if she was with her mom in Bampton when the girl ended up in the river, how would she have floated upstream to end up at the Swann? Rita and Henry also have doubts since Robin and his supposed wife seemed very rehearsed.
Lilly is also unhappy since she thought the Vaughans were good caretakers, Vic beats her and raped her when she gets home, which he does sometimes. He is only her brother because her mother married his dad a long time ago.
Robert is also doubtful of his son's claims. He knows the were acting weird. He also finds a photo of his stolen pig at the fair. There's a shadow of a person next to the pig.
The fake fortune teller guy finds Anthony. He says if he gives him a thousand pounds he can get Armstrong to drop his claim. However, Anthony is the only one who is sure the girl is not Amelia. Reluctantly, with the help of a grief specialist (Mrs. Constantine) he is finally able to admit to himself that he knows Amelia is dead because he found her body. She was kidnapped and he paid the ransom but she was killed anyway.
Rita and Henry are sad they can't see the girl anymore. They kiss. Rita also mentions Helena is pregnant. Henry is supposed to take a photo of the Armstrong family, including the girl and the both go. There, Robert asks about the pig photo, which Henry took. Henry vaguely remembers the guy who had the pig and describes him. Bess tells Rita and Henry that she has an all-seeing eye (she has one glass eye) and knows that the girl is not Alive and that she is feeling lost.
Rita and Henry also do another experiment, this time with ice cold water. After being submerged, Henry's heart stops for 3 seconds before his heart rate rises rapidly.
Anthony tells Rita and Henry what he know, and they go off to search for answers. They see out Ruby, who had been Amelia's nanny and the one who was supposed to be watching her. They talk to her grandmother, noting that the have an idea for how Ruby can help them get to the truth. They announce a Magic Lantern Show that Henry will hold at the Swan. On the poster it mentions a Sapient Pig and someone who will reveal the future.
Everyone is gathered at Swan Inn and the show starts. Maude the Pig's daughter is there (Mabel) who looks exactly like her. Ruby start off the show and begins acting out the story which is illustrated by the acting and photographs. As part of the show, Ruby asks for her fortune from a fortune teller, who tells her to look in a well at a specific time to find out who she will marry. She looks! There's no one! (In other words, Ruby is showing that she was lured away from the baby by someone claiming she needs to go to a well to find her future. That's when the baby was kidnapped.)
The show continues: Then they see someone kidnap a baby and the Vaughans recieve a ransom note. They see them heartbroken. (In other words, they let everyone know what happened to Amelia). Then, the words "WHO KIDNAPPED LITTLE AMELIA?" appear. This is followed by the picture of Maude with the shadow next to her. (In other words, the kidnapper is whoever's shadow it is). From there, the crowd starts trying to remember what the guy looked like who was with the pig at the fair. They start offering up bits and pieces of information.
But the show's not over: Suddenly, a ghostly visage of Amelia appears. Ruby talks to her and asks her to tell them who killed her. The ghost points to the audience. This prompts Lilly to say to herself that she didn't mean to do it and run away in fear. She leaves her puppy behind.
Rita and Anthony go to return her puppy to her. Lilly is ranting about her guilt and Anthony sees that she has Maude. Lilly confesses...but it's about drowning Ann. When she was a kid, she climbed into a sack and Lilly accidentally drowned her thinking it was a piglet she was going to prepare for dinner. Finally, she mentions that Vic was the one who brought Maude over.
The search for Vic begins. Vic goes into the water to hide and thinks Quietly is taking him to safety. In the end, they can't find him, but he's assume he's dead by now.
The parson looks into Lilly's story. It turns out it really was a piglet. Vic was the one who told Lilly it was her sister, but he was lying. Lilly ran away and her sister was found a few hours later, but died of a fever soon after.
Helena and The Girl
Helena is going into labour, while the girl has gone off to the river but it's starting to flood so some people go to look for her. Henry is passing by and helps to get Helena in a boat so they can go to the Swan where Rita is. Joe who has been sick this whole time is dying. Rita's at the Swan taking care of him. At the Swan, Joe dies and the baby is born. Helena tells Rita the girl was always happier with her and that they belong together.
People are still searching for the girl, but finally the innkeeper's son says he saw the girl. After Joe passed, Quietly showed up and the girl told him to tell everyone that her father came for her.
At the Armstrongs, there's been an incident. Robert finally refused to give Robin any more money and he threatened his sister with a knife and cut her. He then ran off, leaving a message that if he doesn't get the money, he's dead. Robert goes to look for him.
Robin is waiting for the person he owes money to. Robert gets him to admit that the whole thing with the girl was to extort money to pay his debts. Robin confronts Robert about who is real father is. Robin once read a letter about an inheritance indicating that "Lord Embury" was his father and he has always believed they were withholding money from him. Robert corrects him -- Lord Embury is Robert's father, he wasn't withholding anything. Robin misunderstood the letter (Robin's legal name is also Robert).
Robin's creditor shows up -- it's Vic. He's alive. Vic butts into their conversation and it's revealed that Vic is Robin's father. Vic met Robin and befriended him and convinced him to steal the pig. Robin was the one who lured Ruby away and who kidnapped Amelia. She was in a sack, but the sack dropped into the water and she died. Vic has been stealing Lilly's money to fund Robin's gambling problem.
Robin attacks Vic with the knife, they tussle into the water as the flood rages. They both die, and soon the ferryman comes to fish their bodies out of the water. Robert begs Quietly for Robin's life, but he ignores him.
At the Armstrongs, Bess tells Robert there was nothing he could have done. There's a knock and two kids are there. It's Ben, who has run away from his abusive father, and he's brought along Alice. They first think he's a boy, but he cut her hair so they could travel safely. When he first ran away, he ended up in a boat, and a boatman ended up telling him about an orphanage and a girl he'd dropped off there. Ben had remembered Robert was looking for her. They quickly decide Ben can stay with them.
Even now, Rita and Henry still puzzle over the science of the girl coming back to life (if that is indeed what happened), but have no firm answers. Rita and Henry marry, and Rita's with a child they are sure is a girl. Other stories come up about the girl from time to time -- perhaps she is with the river gypsies and whatnot. Some say she's been sighted helping to ferry people safely across the waters.
See Once Upon A River