With only a commonplace name, an old address and dim memories as leads, Veronica and Wallace attempt to help classmate Justin Smith find his father John, who disappeared 10 years earlier.

Meanwhile, as Veronica faces some complicated feelings towards ex-boyfriend Duncan and new romantic interest Troy, guidance counselor Rebecca James calls Keith to the school to discuss the recent, dramatic changes in his daughter's life. Later, Duncan struggles with ways to cope with his sister's death as the anniversary of her murder approaches.

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.

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.