The musical starts when Sam Wheat and his long-time girlfriend, Molly Jensen, move into a loft apartment in Brooklyn together ("Here Right Now"). Sam is a banker, Molly a sculptor, and their friend Carl Bruner is introduced as one of Sam's co-workers, come to help them settle in. The three of them seem to be a tight-knit group, with Sam and Molly very much in love. However, Sam clearly shies away from the word, which makes Molly visibly uncomfortable. She starts to say something about it, but soon stops herself, and Sam distracts her with a rendition of "Unchained Melody," leaving her insecurities temporarily forgotten.
At work, Sam notices some discrepancies with several accounts and is unwilling to let them go, despite the fact that he has a date with Molly that evening ("More"). He confides in Carl with his discovery, and his friend not only agrees to keep the findings a secret, but promises to investigate himself, so Sam can keep his date. Thanking him, Sam leaves, and meets up with Molly, who later confesses that she wants to marry him. Sam is taken aback and Molly suddenly asks why he never tells her that he loves her ("Three Little Words"); he assures Molly that he doesn't say it in so many words because he prefers to say it through his actions. Molly tells him that she'd still like to hear it every now and again, but his reply reassures her nonetheless. However, they're soon approached by an armed man that tries to steal Sam's wallet. Sam fights back instead of surrendering, and the two struggle for the gun. It goes off and Sam is fatally shot, leaving Molly to cry out for help ("Sam's Murder"). Instead of moving on, however, Sam becomes a ghost, and he stays behind with Molly instead of following the light; unable to leave Molly, he follows her to the hospital, and another ghost explains what he's become ("Ball of Wax"). A trapped Sam struggles to reach out to Molly ("I Can't Breathe").
Back at the apartment, Carl helps Molly clear out some of Sam's old things; clearly, she's hesitant to let go, totally unbeknownst to the fact that Sam is very close by, unable to move on himself. When she's alone, the man that killed Sam sneaks in and begins to ransack the place while Molly is upstairs, forcing Sam into a panic that he'll hurt her, too. Sam manages to spook the man and he flees. Needing to know who he is, Sam pushes himself through the front door with great effort, and follows the man all the way back to his own apartment. He finds out that the man's name is Willie Lopez, and that he'd eventually go back for what he was looking for. Desperate, Sam then seeks out a psychic, Oda Mae Brown, who seems to be a total fraud ("Are You a Believer?"). By some miracle, she actually hears Sam, and he convinces her to go talk to Molly on his behalf - by singing '10,000 Bottles of Beer on the Wall' obnoxiously, no less. In the meantime, Molly is grieving and not taking the loss very well ("With You"). She gets a visit from Oda Mae, but Molly is hesitant to believe, until Oda Mae starts parroting things that only Sam would know. Eventually, she comes around, and agrees to listen. Through Oda Mae, Sam tells her that he was set up, murdered, and that she needs to go to the police; Oda Mae bails as soon as she hears the word. Molly takes this information to Carl, who tells her that it's crazy, but promises to check it out. She goes to the police and Carl goes straight to Willie's place where a distraught Sam discovers the truth, in that his murder was at Carl's own error. As Molly swears to suspend all disbelief, a drunken Carl wonders the streets trying to convince himself it was not his fault ("Suspend My Disbelief/I Had a Life").
At the police station, it's revealed that Oda Mae has quite the criminal record. Shaken, Molly leaves there with the knowledge that the psychic is a fraud and she loses hope, much to Sam's dismay ("Rain/Hold On"). Molly in her anger sits down to do some pottery as the radio plays. Static is heard and Molly gets up to change to station, as she turns the dial Unchained Melody is suddenly heard. Molly quickly turns off the radio in shock. After a moments pause she turns it back on and slowly returns to her pottery. Sam, who is watching, approaches her from behind singing along, longing for her touch. Just as Molly begins frustrated and starts to lean back as if she can feel Sam, there is a knock on the door. It's Carl. Molly tells Carl that he was right, that the whole thing was crazy, and that she was just grasping at straws. He assures her that it's only natural, but she has to move on, and he even makes a poorly received move on her ("Life Turns on a Dime"). Enraged, Sam manages to break something, and a flustered Molly asks Carl to leave.
With the help of another ghost on the subway, Sam learns how to move objects ("Focus") and returns to Oda Mae's place to enlist her help once more ("Talkin' Bout a Miracle"). Suddenly, Oda Mae is a legitimate psychic, with the ability to call on other spirits instead of resorting to fraud. While Sam is there, Willie Lopez finds her, and she has to run for her life. Sam uses his newfound abilities to spook him and chase him away, but Willie runs into traffic and dies. Unlike Sam, he is not offered a white light, but it's implied that he's dragged somewhere completely different. However, Sam knows that it isn't over, and he begs Oda Mae to help him stop Carl from getting to the money, in order to protect Molly.
We then see Molly, trying to get her life together and move on ("Nothing Stops Another Day"); it's seen that she's selling pieces at her gallery and she apologizes to Carl for pushing him away. Carl, meanwhile, is anxiously awaiting a call and waves her off under the guise of having a busy day. Together, Sam and Oda Mae break into the account that Carl was extorting, Sam feeding her account numbers and information while she poses as 'Rita Miller.' The account is closed and Sam goes to find Carl in his office, in a panic. Moving objects around the room, Sam scares Carl, moving objects around again and making it clear that he knows what really happened. Scared, Carl tells Sam that he'll kill Molly if he doesn't leave him alone and get him the money. However, Sam runs back to Oda Mae.
When she's handed a check for around four million dollars, Oda Mae tries to take the money and leave the situation for good ("I'm Outta Here"), but Sam convinces her to donate the money. Sam then takes her to go see Molly again in order to warn her about Carl. At the apartment, Molly tries to send her away at first, but Sam is able to walk through the door and tell Oda Mae the significance of the earrings Molly is wearing, as well as read a letter for Sam that Molly has inside the apartment. After Oda Mae repeats these things, Molly is able to believe again, and she lets the psychic in. She explains everything to Molly, who is clearly emotionally distraught, and Oda Mae even lets Sam use her body to hold Molly and comfort her ("Unchained Melody (Dance)")
Carl comes into the apartment, armed and frightened for his own life; he owes dangerous drug dealers money and he's desperate. Even though it's clear that he doesn't want to resort to such measures, Carl grabs Molly and holds his gun to her, telling Sam that if he doesn't have Oda Mae tell him where the money is, he's going to kill her. There's a struggle, and Carl is killed, and he's dragged away in the same way as Willie.
Now that Carl is gone and Molly is safe, the light returns for Sam and Molly is able to see and hear him. Knowing that it's time for him to go, Sam says goodbye to Oda Mae, and regretfully turns to Molly. They're able to say their goodbyes, Sam finally telling Molly that he loves her in the way that she wants to hear ("The Love Inside").