The series depicts the adventures of Veronica Mars (Kristen Bell) as she deals with life as a college student while moonlighting as a private detective.
The episode is the second of two to deal directly with the death of Hearst's basketball coach, Tom Barry (Matt McKenzie).
In this installment, Veronica and Keith (Enrico Colantoni) search for Tom's missing son Josh (Jonathan Chase) while investigating a variety of alternate suspects.
Meanwhile, Logan (Jason Dohring), Parker (Julie Gonzalo), Mac (Tina Majorino), and Bronson (Michael Mitchell) attend a scavenger hunt for Valentine's Day.
"Mars, Bars" marks the final appearance of series Michael Muhney, the actor of Sheriff Lamb, after the death of his character.
At the end of the previous episode, Postgame Mortem, Veronica is arrested by Sheriff Lamb (Michael Muhney) on the suspicion that she helped the now-missing Josh Barry to escape from prison.
Cliff McCormack (Daran Norris), a local public defender, also arrives, and tells Veronica that she has been all but cleared, but Sheriff Lamb will keep her in custody for as long as he can because he still believes she was involved in Josh's disappearance.
Keith returns to Mars Investigations, where Hank Landry arrives and says that he found a bugging device in his phone.
Landry had been implicated in the ongoing investigation into the death of Cyrus O’Dell, dean of Hearst College where Veronica is a student.
Keith brings his findings on the death of Cyrus to Sheriff Lamb and provides an alternate explanation; that the Dean had discovered his wife was having an affair.
While reviewing the O'Dell case, Veronica notices that the TV station the dean was watching the night he was murdered had moved its programming back an hour, meaning their estimated time of death was wrong.
Inside is a DVD of Coach Barry telling Josh about his condition and that he was planning to have a friend kill him to avoid futile medical expenses and give his family the insurance money.
He enjoyed the scene for showing Neptune as a California beach town while distinguishing itself due to the cold weather, a visual characteristic that he felt was not portrayed often enough.
[8] The reveal of Sheriff Lamb's death was not leaked anywhere online prior to the airing of "Mars, Bars", something about which Muhney was happy.
[12] Thomas praised Daran Norris's performance in the episode, particularly his voice in the scene in which he defends Steve Botando in front of Sheriff Lamb.
[15] He referred to "Mars, Bars" as one of the finest episodes of season three, praising the Valentine's Day subplot, the development of the mystery of Dean O'Dell's death, and Muhney's performance.
"[15] He also praised Lamb's death scene as being devoid of clichés by not giving him an act of heroism for his dying moments.
Regarding Lamb, she opined that it made her realize how much she had enjoyed the role; however, she thought that "knowing that the show is almost finished limits its impact.
"[18] She was positive towards Keith's role in the episode but referred to the Valentine's Day plot as out of character for the show for its happy feel.
[21] After the series was announced as being cancelled by The CW, fans collectively sent nearly 10,000 Mars bars to Dawn Ostroff, the president of the network as a reference to the show, but the attempt was futile.