Sandy finds Kirsten in the bedroom as Seth finds Ryan in the pool room. Seth admits to Ryan that he started the fire, but it was an accident. Sandy laments that he thinks Seth is hiding something, but after their fight earlier, now isn't the time to doubt his honesty. Seth wants to get his iPod from the car so he can listen to some mopey music, and Ryan remembers he left it parked outside of Volchok's target. Ryan heads out to get the car and that's when Volchok rushes up to him. He ditched the car and ran. He tells Ryan he needs to get out of town, but he needs some money. And if he goes down, Ryan goes with him. Who knew a few punches could get a guy so deep?
Summer, Marissa and Taylor decorate the bleachers for the graduation ceremony. Julie finds her daughter and hands her a graduation gift from Jimmy. A letter. Dawn arrives at the Cohen home for the graduation. Ryan happily hugs his mom. And Caitlin arrives home, her new home, also for the ceremony. Julie suspects Caitlin has more in mind that a simply sisterly gesture.
Seth finds his father upstairs and confesses that he burned down the Newport Group with a wayward roach. Although disappointed, Sandy understands. He's good that way. At Harbor, Marissa tells Summer what the letter was about. Jimmy is working on boats sailing to the Greek Islands and has invited her to join him for a year. She'll be doing hard work, peeling potatoes and pitting olives and such, but she thinks it'll be a good break from the hullabaloo of Newport. Thing is, she has to fly out tomorrow night to catch up with the boat in Hawaii. Summer makes her promise that she'll sail to Rhode Island one day.
Volchok hides in a van, waiting for a friend to bring him some clothes from the loft. The girl wonders why Volchok hasn't just left yet, then realizes he wants to see Marissa one last time.
It's graduation time. Before the ceremony, Marissa pulls Ryan aside and tells him about her plan. He thinks it sounds great. Just great. As long he can drive her to the airport and be the last person to say goodbye. The ceremony finally arrives and the Class of '06 is handed their diplomas.
That night, the Cohens, Robertses, Coopers and Atwoods gather for a celebratory dinner at The Yacht Club. After the meal, Marissa pulls Julie aside and mentions Jimmy's letter to her. But Julie already knew, as Jimmy called her last week for he thoughts on sailing before sending the letter. And Julie thinks that if this is something Marissa wants to do, she's happy to let her go. Julie then gives Marissa her graduation gift, a pearl necklace.
Out in the parking lot, Dawn is giving Ryan his own graduation gift. An old Toyota Land Cruiser. She's been saving up for a little while and her boyfriend Ron knows a guy who restores cars. Ryan is astounded by the gesture. Then Marissa gets a call from Volchok. He tells her that if he can't see her one last time, he's going to make life rough for Ryan. If she doesn't believe, ask Ryan about the car they stole. So she does. Ryan says he needs money to help Volchok get out of town, so Marissa gives him the necklace, figuring they're in this together.
The next morning, Ryan picks up Marissa for one last drop off with Volchok. After a pit stop at the pawn shop, of course. Marissa asks if she can come along, and Ryan resists. But he relents after saying she has to stay in the car the whole time. Elsewhere, Sandy drops by the DA's office. And at home, Kirsten hands Seth an envelope from RISD.
Ryan exits the pawn shop and finds Volchok waiting for him. The money exchange is civilized, if chilly. Then Volchok sees Marissa behind the wheel of Ryan's car. He slams on the window and begs to talk to her, but she simply drives off. Volchok screams in a rage.
Later, at home, Julie comes in as Marissa is packing to leave. On the verge of tears, Julie apologizes to her daughter for sleeping with one of her ex-boyfriends, and framing another for attempted homicide. Despite the colorful and non-traditional offenses, Marissa forgives her mother.
That night, the gang of four gets ready to say goodbye to Marissa. But before they do, Marissa has one last place for the group to visit. Sandy catches up with Kirsten and tells her that he talked to the DA, and since The Newport Group won't presses charges against Seth, the whole thing is over.
In two cars, the group pulls up to the model home that Ryan and Luke accidentally burned down three years ago. The one that was completely renovated and Marissa passed out in a few months ago. And she still wants to go back inside. The kids hop the fence and go for a swim in the pool. After some cannonballs and some laughs and some tears, Ryan and Marissa head for the airport. Volchok and his friend, sitting in his van, watch them go. Volchok takes a swig from his flask and hits the gas.
Seth takes Summer into his bedroom and shows her his mail. Although his application arrived too late for the fall semester, RISD has accepted him for the spring. He starts in January. He apologizes to Summer for screwing everything up with Brown.
As Ryan drives, Volchok rams his car from behind. He then pulls alongside and tries to run Ryan off the road. And he succeeds. Ryan barrels through a curve and over an embankment. The car rolls end over end down the hill, finally crashing on another road below. Coming back to his senses, Ryan crawls out of the car. Noticing gas pouring from the tank and a small fire, he grabs an unconscious Marissa and carries her free of the wreckage in a mirror from the time he found her in Tijuana. The car explodes and Ryan lays Marissa down on the pavement and rouses her. He tells her he's going to get help, but she begs him to stay. And then she dies.