When people die, their souls end up on the mountain of Purgatory, where sins are rehabilitated before entering Heaven. It’s an ancient bureaucracy, overseen by one Angel and staffed by caseworkers—people who denied their sin and refused to participate in their rehabilitation.

Amelia Morgenthal is Purgatory’s longest-serving caseworker. Normally, the new souls she oversees arrive unconscious, but Rosealie Durant appears screaming and wild, calling out for a man named Max. Per protocol, Amelia wipes Rosealie’s memories of her last 24 hours on Earth. She thinks the problem is solved, but then Tad, the overseeing Angel, shows up. He seems to recognize Rosealie and he strikes a bargain with Amelia: if she guides Rosealie through Purgatory and manages to keep the Memory Wipe a secret, she will be released from caseworker duty.

Rosealie awakens and Amelia explains the mountain—each tier rehabilitates one sin: the lowest is Pride, then Envy, Wrath, Sloth, Greed, Gluttony and Lust. A soul can leave their assignment, but they can only travel down the mountain, not up. Rosealie is assigned to complete Envy and then Lust. Amelia pores over Rosealie’s file, determined to help, but her case history is mysteriously blank. All the usual information is gone, leaving Amelia with only one clue: Max. 

Up in Envy, Rosealie is having trouble adjusting. The assignments keep dredging up memories of an ex-boyfriend. He cheated on her and walked out of her life a year before she died, and she knows that in the end she was better off without him. Amelia discovers that Max is the ex that Rosealie resents so much, and realizes that the Memory Wipe erased their reconciliation.

Max is still alive. He’s moved halfway across the world to escape reminders of Rosealie, but his life is still miserable. In a drunken stupor, he dies in an accident. When he arrives in Purgatory, he is ecstatic—this is his chance to find Rosealie and be happy again. He is assigned to Pride and begins his search.

Tad arrives with new orders for Amelia—play matchmaker by reuniting Max and Rosealie. Amelia is hesitant; she wants to know more about what happened on Rosealie’s last day before she acts. In the course of her research she discovers that the couple share a fated love that has endured over many lifetimes, and that they have become entertaining playthings for the beings in Heaven. Now she has to weigh her choices: she can betray her new friend for her own benefit, or follow her conscience.

Max escapes from Pride and forces his way up to Rosealie. He finds her, but as soon as he touches her, she screams and falls to the floor unconscious. While she is knocked out she sees a vision of one of her past lives. She awakens to discover that she has been released from Envy, but a new punishment has been added to her sentence: she must now spend time in Greed. Amelia is unnerved—too many inexplicable things are happening. She doesn’t know how Max escaped, or why time was added to Rosealie’s sentence.

In Greed, Rosealie is plagued by more dreams of past lives. She begins to suspect that she is being manipulated by Heaven, and she starts forming a plan to win her freedom. Amelia too, is trying to piece together the mystery, when suddenly she is released from caseworker duty. It is something she’s wanted for decades, but she is dissatisfied, because it means she will no longer have the resources she needs to help Rosealie.

Max is forced to reexamine his time with Rosealie and he considers the possibility that she may be better off without him. His relentless drive to possess her is replaced by a yearning to finally apologize for all his transgressions. He reunites with Amelia, and they form a tenuous alliance. 

Heaven is unhappy with the turn of events; they want Rosealie and Max to be together. They send another Angel, Vita, down to the mountain to meddle with Max and Rosealie’s rehabilitation, and when Tad protests out of a sense of duty, they incapacitate him. Vita intercepts messages from Rosealie, using them to sow distrust between Max and Amelia. Now in Lust, Rosealie knows she wants to be free, but she doesn’t know how to fight against Heaven. Vita confronts her, telling her that she and Max can never rest, that it is their duty to experience all forms of love so Heaven can watch. Rosealie rebels and through clever manipulation, she frees herself from Purgatory.

Amelia and Max arrive in Lust, disappointed to find that Rosealie is already gone. Vita releases them—she is convinced that if Max and Rosealie reunite, things will go in Heaven’s favor. On the peak of Purgatory, all of the memories of past lives come rushing back to Max. He is like a different person, an amalgam of everyone he’s ever been, and Amelia barely recognizes him. She realizes the same thing must have happened to Rosealie-- all of her progress, her drive to be free, must have been diminished by the memories of hundreds of happy lives.

They find Rosealie; she is ready to have another life with Max, opting for familiarity over freedom. Amelia pushes back, reminding Rosealie and Max of all the things they learned, and in response Vita arrives and threatens to destroy Amelia’s soul. But the Angel has miscalculated—now that her memories have returned, Rosealie recognizes her. Vita is one of Rosealie’s own past lives, the first to form a bond with Max. When Rosealie died and Amelia wiped her memory, her old soul was fractured. The older pieces of Rosealie yearned for their relationship with Max and manipulated everyone in order to restore the bond. 

Now that Rosealie knows the truth, she convinces Max that they should separate. He goes back to Earth with Amelia, and Rosealie travels to Heaven to try to repair the damage her split soul has caused.