Warning: This section contains spoilers for all six books in The Mediator series!
Suze first meets Jesse when she arrives at her new home in Carmel and enters her bedroom for the first time. She immediately sees Jesse sitting on her window seat, although Jesse is not aware that she can see him. Suze, frustrated that she is already encountering ghosts on her first day in her new home, goes on the attack as soon as they are left alone, demanding to know who the hell he is. Jesse is startled by the fact that she is addressing him, but attempts to make friendly conversation while Suze tells him in no uncertain terms that he needs to "clear out." This leads to sparks between the two when Suze basically orders him to move on or get out, whereas Jesse claims to like "hanging around" and has no intention of leaving.
After their initial encounter, Jesse tries to avoid materializing in Suze's presence (although he does make his presence known in subtle ways, such as opening her windows during the afternoon and closing them again when the fog starts to roll in every night) until Suze attempts to sneak out of her house to confront the ghost of Heather Chambers. It turns out that Jesse has been following Suze, and is concerned for her safety, as he knows Heather to be a more powerful and wrathful ghost than any Suze has encountered in the past. Jesse's concern only proves to infuriate Suze more, who storms out of the house despite his warnings. However, when she gets to the school, she realizes that Heather is as dangerous as Jesse warned, particularly when Heather flings the solid bronze head of a statue of Junipero Serra at Suze. Fortunately, Jesse appears and holds Heather off long enough for Suze to escape, and bandages the wound she got while trying to escape Heather's wrath. After this, Suze begins to appreciate Jesse's presence more, and they begin to have a more friendly relationship...although Suze still is not interested in following any of Jesse's advice.
At the end of ther first book, Suze, having had her belly full of Heather's shenanigans, decides to exorcise the ghost. Jesse is worried for her safety, but Suze point-blank warns him not to go anywhere near the school while she is performing the ceremony in case he accidentally be exorcised as well. Jesse heeds her warning, but is still concerned and thus warns her stepbrother "Doc" that Suze is in danger. Doc has always suspected that their home was haunted, and so heads to the school with his older brother in time to save Suze from Heather's final attack. After this, Doc realizes that he was right about the presence of a ghost, and further deduces that Suze can see him. With Doc now in on her secret, the two of them manage to work out Jesse's identity and learn the secret of his death.
Over the next two books, Jesse and Suze grow to become close friends, with Jesse helping Suze with her mediations using his kinetic powers. During this time, Suze begins to feel herself getting a small crush on Jesse, which she resists vehemently on the basis that they could never have a future together...if he even likes her that way in the first place. However, towards the end of the third book, Suze's best friend Gina reminds her that a psychic (the same psychic who had correctly identified Suze as a mediator) had predicted years ago that Suze would have only one love in her life, but that it would "last until the end of time." Suze reluctantly begins to realize that this prophecy can only refer to Jesse. This suspicion is confirmed at the end of the third book when, while Jesse pays her a visit in the hospital after a mediation gone awry, Suze realizes that she has fallen in love with him.
In the fourth book, the truth behind Jesse's mysterious death becomes perfectly clear when Suze's stepfather discovers Jesse's body buried in their backyard. Suze had been fearful that this discovery would liberate Jesse's soul from this world and he would pass on; and though Jesse promises that he will not leave even if his body is found, he disappears as soon as the body is recovered. Suze falls into a deep state of grief and vows to get revenge on his murderers, the ghosts of Maria de Silva and Felix Diego. She soon learns, however, that Jesse did not pass on because of the solution of his murder: he was exorcised by a young mediator on the request of Maria herself. Suze, refusing to allow Jesse's life to be stolen from him again, has Father Dominic send her spirit to the other world to bring Jesse back. While in the other world, Suze and Jesse also encounter another mediator--Paul Slater, the brother of the young mediator who had inadvertently exorcised Jesse. Paul has his sights set on Suze, and he and Jesse take an instant dislike to each other.
Once Suze and Jesse return from the other world and defeat Maria and Felix Diego, things start to look up for them--especially when, at the end of the fourth book, Jesse kisses Suze. This kiss, however, is accidentally interrupted by Doc; and, much to Suze's chagrin, Jesse begins acting distant with her afterwards.
The strain on their relationship is compounded when Paul Slater transfers to Suze's school and begins trying to turn Suze's feelings away from Jesse and towards himself. Suze's friend CeeCee overhears Paul mention Jesse and realizes that Suze must have a crush on him. This proves to be crucial later when CeeCee shows up at Suze's house while Jesse is in the room and simultaneously reveals to an invisible Jesse that Paul Slater has been romantically pursuing Suze, and that Suze has been resisting his advances because of her feelings for Jesse. Jesse vanishes from Suze's room in the midst of this and doesn't reappear for a few days; Suze learns from Father Dominic that this is because Jesse feels that he can no longer live with her and has moved into the rectory. Suze is overwhelmed with both anger and disappointment, thinking that Jesse regrets kissing her and is trying to break it off with her by moving out.
Later that day, Jesse appears in Suze's room to collect his cat and say goodbye. He starts to explain his reasoning to Suze when Paul Slater shows up and starts trying to goad Jesse by insinuating that Suze has been behaving promiscuously with him behind Jesse's back. Jesse becomes enraged and attacks Paul; Suze tries in vain to break it up, and the two of them manage to take the fight out of Suze's room and downstairs, where Suze's stepbrothers are throwing a party. The fight gets so violent and destroys so much of the house that Suze finds the only way she can stop it is to grab Paul and shift him to the other world. This causes her to lose consciousness, snapping Jesse out of his blind rage. It's at this time that CeeCee realizes that Jesse is a ghost, since she saw an invisible force beating the snot out of Paul as Suze screamed his name.
When the aftermath of the fight has blown over, Suze starts trying to cope with the fact that Jesse is no longer going to be living with her. Deep in thought, she wanders into the Mission's cemetary and finds that Jesse is standing in front of the grave that Suze had commissioned for him after his body was found. There, he explains to Suze that the reason he became so distant after their first kiss was not because he didn't love her, but because he did love her and felt that she deserved a real life with a real boyfriend. He also explains that he only moved out because he felt it was inappropriate for him to be sharing a bedroom with a girl that he was in love with. The two of them kiss, and this time no one interrupts them.
Unfortunately, Paul Slater is not content to let Suze and Jesse be together. He discovers that he and Suze have the power to go back in time, and intends to prevent Jesse's murder so that he and Suze will never meet. Suze is frantic to stop him because she doesn't want to live in a world without Jesse. Despite her attempts to stop him for carrying out his plan, Paul travels back in time, so Suze travels back as well to intercept him. There she meets Jesse before he was murdered and realizes that she cannot deny him his chance to live a full life, and helps Paul prevent Jesse's murder. In the midst of this, however, Suze and Jesse become trapped in a burning barn and Suze is forced to shift forward in time, accidentally bringing Jesse's body back with her.
Surprisingly, it seems that this action did not alter history, but perhaps created an alternate history: Jesse's ghost is still in the modern day with no changes in his memory of his own murder and the past 150 years a spirit; while simuntaneously, Jesse's living body has been transported to the present day but is dying because it lost its soul during the time shift. Suze is overwhelmed with grief because she believes that this means that she will lose Jesse once and for all-- his body will die and his soul will cease to exist. But when Jesse's ghost touches his soulless body, his spirit returns to the body with all his memories of Suze and his time as a ghost intact. Furthermore, he soon realizes that he now is a mediator as well. The series ends with human Jesse meeting Suze's family and taking her to the Winter Formal.