Pretty Little Liars is a series of young adult novels by Sara Shepard. The series follows the lives of four girls — Spencer, Hanna, Aria, and Emily — whose clique falls apart after the disappearance of their leader, Alison. One year later, they begin receiving text messages from someone using the name "A" who threatens to expose their secrets — including long-hidden ones they thought only Alison knew.[1] Originally developed as a television series by book packaging company Alloy Entertainment, the idea was described as "Desperate Housewives for teens."[2] Alloy met author Shepard and gave her the property to develop into a book series.[2] The first novel, Pretty Little Liars, was released in October 2006.[1] It was followed by Flawless and Perfect in March and August 2007,[3][4] Unbelievable and Wicked in May and November 2008,[5][6] Killer in June 2009,[7] and Heartless in January 2010.[8][9] An eighth installment titled Wanted is set to be released in June 2010.[10] ABC Family began casting for a Pretty Little Liars television pilot in October 2009,[11] and in January 2010 the network picked up the series for 10 episodes, to premiere on June 8, 2010