In the shocking, action-packed season finale, a determined Veronica must betray someone she cares deeply about in order to solve the season-long mystery of who murdered her best friend Lilly Kane, but what she discovers puts her life in serious danger. Meanwhile, on the eve of a reception for the Governor of Calif., Jake Kane asks Duncan if he really wants to know what happened on the night Lilly died. Later, Keith awaits the results of a paternity test.

After discovering the true perpetrator of the bus crash, Veronica is desperate to warn others before it's too late. However, she inadvertently puts herself and her loved ones at risk in the process. Meanwhile, Keith tracks down Woody in hiding, Wallace leaves for Paris to be with Jackie, and Weevil again runs into trouble with the law.

Determined to get to the truth behind who drugged and assaulted her at a party the year before, Veronica questions her friends and many rivals about the chain of events that night at Shelley Pomroy's house. Meanwhile, when one of Veronica and Wallace's stunts affects her job at Kane Software, Alicia confronts Keith about his daughter's behavior. Later, in an attempt to get closer to his son, Aaron throws a birthday party for Logan that inadvertently surprises everyone.

Veronica and Keith launch their investigation. Their involvement puts Police Chief Langdon on edge. Penn goes public with his theory on who the bomber is. Meanwhile, local teen Matty Ross begins her own search for her father’s killer.

When Duncan disappears with Meg's baby, Lamb must work with two FBI agents to extract as much information as possible from an uncooperative Veronica. Meanwhile, Wallace reveals the real reason he returned to Neptune, and Weevil and Logan make a breakthrough in their hunt for the rogue gang member.

After the campus rapist anonymously announces the location of his next rape, Veronica hires her friends to help her track him down, but is shocked when she discovers the rapist's identity. Meanwhile, Logan makes a drastic decision about his future with Veronica, and Dean O'Dell hires Keith to prove that his wife is unfaithful.

When Weevil's poker winnings go missing after a game at Logan's place, Veronica questions each player to piece together the evening's events and catch the thief. Meanwhile, on the eve of the Echolls' annual Christmas party extravaganza, Keith is hired by Lynn Echolls to track down one of her husband Aaron's potential stalkers.

A series of fire drills leads Veronica to discover that Neptune High has been receiving bomb threats, so she enlists Wallace and Mac's help to investigate classmates who could pose a serious threat to the school, including new student Ben. Meanwhile, Keith stuns Veronica with the news of who he's been secretly dating. Later, Duncan confronts Veronica about her ongoing investigation into his sister's death.

The campus newspaper hires Veronica for an undercover expose on the Zeta Theta sorority sisters during rush week to investigate Parker’s rape. Veronica begins to realize though that not everything is as it appears in the sorority house. Logan and Wallace take part in a challenging Sociology class role-playing experiment as prisoner and prison guard, and Keith treks through the desert after escaping from the scene of a crime.

While trying to navigate the everyday drama of high school, the smart, fearless, 17-year-old Veronica Mars also moonlights as an apprentice private investigator out to solve her wealthy town of Neptune's toughest mysteries. After coming to the aid of the new kid, sophomore Wallace Fennel, who's been duct-taped to the school's flagpole, Veronica ends up incurring the wrath of the thugs who put him there, Eli "Weevil" Navarro and his P.C.H. Biker Boyz. To get Weevil and his gang off her and Wallace's case, Veronica devises an intricate plan that helps some of Weevil's cronies avoid trouble with the law. Meanwhile, defying her father, Keith Mars, the disgraced former sheriff turned private eye, Veronica pursues a late-night case of adultery against billionaire Jake Kane, only to make an unsettling discovery about her mother, who abandoned Veronica and Keith a year ago.

To help restore a cheerleader's ruined reputation, Veronica turns to funky computer geek Mac to find the hacker responsible for leaking the embarrassing, private results of a popular online "purity test" to all of Neptune High. Meanwhile, Keith helps Wallace and his mom with an unruly tenant in their building. Later, to get answers about Lilly's murder, Veronica attempts to visit Lilly's confessed, condemned killer Abel Koontz in prison.

When one of Neptune High's haughtier students brings a sexual harassment suit against a favorite teacher, Veronica finds herself pitted against her father when the girl's parents hire Keith to help in their case. Meanwhile, with the tabloids claiming his mom is still alive, Logan turns to Veronica to help him track down the truth. Later, Veronica discovers more unsettling information about Duncan's hidden medical condition.

Veronica takes the stand in Aaron Echolls's murder trial, and is distracted during final exams while waiting for the verdict. Meanwhile, Keith takes new evidence about the mayor to Lamb, and Weevil asks Mac and Cassidy for help to pass algebra.

Weevil asks Veronica to clear his name after he's arrested for selling fake debit cards to Hearst students, claiming he's being framed because of his criminal background.

Convinced the bomber is still at large, Veronica visits Chino to learn more about Clyde and Big Dick. Mayor Dobbins’ request for help from the FBI brings an old flame to Neptune. Veronica confronts her mugger.

Veronica discovers Keith has been hiding something scary from her. The real reason for Penn’s latest theory on the bomber comes to light. Veronica loses confidence in new friend, Nicole, owner of Comrade Quacks.

As Veronica learns more about Nicole's past, her suspicion deepens. A frantic phone call from Paris leads to a search for Matty. Veronica unwittingly does legwork for Leo.

Veronica uncovers information that her fellow outcast Mac was switched at birth with a more affluent student, causing Veronica to examine her own questions about whom her real father may be. Meanwhile, a serial killer has resurfaced in Neptune forcing Sheriff Lamb to forge a reluctant, tense partnership with Keith. Later, Veronica flirts with a handsome young rookie at the sheriff's department to obtain more information on Lilly's murder.

Veronica surprisingly finds herself working as a "love detective" when she's asked to track down her friend Meg's secret admirer and a Russian bride's estranged fiancé. Meanwhile, after discovering that one of Lynn Echolls' credit cards is in use, Veronica and Logan go to a Los Angeles hotel in hopes of finding her or a clue.

Keith takes on a second concurrent murder case when the head of the Hearst basketball team turns up dead and his son is the prime suspect. Meanwhile, a depressed Logan refuses to leave his hotel room and ends up babysitting Dick's girlfriend's little sister for days.

When Veronica is released from jail, she is contacted by Josh Barry who is desperate to prove his innocence in his father's murder. Meanwhile, Keith gets bittersweet news from the county commissioner, and Logan helps Mac and Parker on a scavenger hunt.

Veronica tries to help her new boyfriend Troy find his father's stolen car and turns to Weevil for assistance, but the situation becomes dangerous when she discovers that Logan and Troy's buddy Luke might have left more than a piata in the car after their night out in Tijuana. While Keith has accepted that his wife is gone and begins dating school guidance counselor Rebecca James, Veronica continues to secretly investigate her mother's whereabouts, leading her to stumble on a secret Lianne Mars was keeping.

After the summer fireworks caused by a dangerous confrontation with Lilly Kane's murderer and a surprising visitor at her door, Veronica attempts to settle into "normal" life, complete with a new after-school job and a return to the popular fold at Neptune High, but she gets pulled back into the investigation business when Wallace is kicked off the basketball team for testing positive for drugs.Meanwhile, Keith sits down with reporter Julie Chen to discuss his new book on the Lilly Kane murder, "Big Murder, Small Town." Later, after seeing his father arrested for murder and being charged and tried for murder himself, Logan seeks refuge from the paparazzi and relaxes poolside at the Casablancas mansion with buddies Dick and "Beaver" and their sexy stepmother Kendall.

When the profits from the Neptune High Winter Carnival go missing, Veronica finds herself defending Jackie from the condemning teachers and students. Meanwhile, Keith meets with her father, Terrence Cook, after he is accused of playing a role in the bus crash, and Logan initiates a new relationship while Beaver continues an old one.

Gia enlists Veronica's help to find out who is stalking her, and Clemmons cancels the senior prom.