what is the storyline of this series?
It revolves around Veronica Mars as a student who progresses from high school to college while moonlighting as a private investigator under the tutelage of her detective father
Veronica Mars
The character Veronica Mars is a student who progresses from high school to college while moonlighting as a private investigator under the tutelage of her detective father. 
when does veronica find out who killed lilly At the twenty-second and final episode of the first season who played these characters? Kristen Bell and Enrico Colantoni to name a few
wiki:14112643
Veronica Mars [SEP] Introduction
The character Veronica Mars is a student who progresses from high school to college while moonlighting as a private investigator under the tutelage of her detective father. In each episode, Veronica solves a different stand-alone case while working to solve a more complex mystery. The first two seasons of the series each had a season-long mystery arc, introduced in the first episode of the season and solved in the season finale. The third season took a different format, focusing on smaller mystery arcs that would last the course of several episodes. Thomas initially wrote "Veronica Mars" as a young adult novel, which featured a male protagonist; he changed this because he thought a noir piece told from a female point of view would be more interesting and original.