The second season of Pretty Little Liars, based on the books of the same name by Sara Shepard, premiered on June 14, 2011 and concluded on March 19, 2012 on ABC Family. It follows the lives of four teenage girls, Aria Montgomery, Spencer Hastings, Hanna Marin, and Emily Fields, who are dealing with the mysterious disappearance and death of their former best friend and queen bee, Alison DiLaurentis, along with other problems in their personal & social lives. Outcomes of Alison's death include messages from an anonymous source that we know as "A". That person knows everything about the girls, including some terrible things that they did in their past with Alison. The second season continues from the season finale of the previous season, in which Ian Thomas, Spencer's brother-in-law, is presumed to have been killed in an incident at the top of a bell tower but is also accused of murdering Alison.
On January 10, 2011 ABC Family renewed the series for a second season. After an initial order of 24 episodes, it was announced in June that a special Halloween-themed flashback episode would air as part of ABC Family's 13 Nights of Halloween lineup, bringing the season 2 episode order to 25 episodes. The season premiere brought in 3.68 million viewers, which was higher than the season 1 premiere. The Halloween special aired on October 19, 2011, drawing 2.5 million total viewers. The second half of season 2 premiered on January 2, 2012.