Who Killed Alison In Pretty Little Liars? Her Mysterious Disappearance Explained

The first three and a half seasons of the hit TV series "Pretty Little Liars" are built on finding the answer to one question: Who killed Alison DiLaurentis? When Alison went missing the summer after her freshman year of high school, her friends Spencer, Emily, Hanna, and Aria grieved for her. They grew apart in the wake of her disappearance, only to be brought back together at the beginning of their junior year when Alison's body was found buried under her parents' gazebo. The girls also started receiving threatening texts and experiencing torment at the hands of a mysterious, malevolent figure known as "A." 

With Alison's murder investigation threatening to light up every secret in Rosewood and A breathing down their necks, Spencer, Emily, Aria, and Hanna spend a year and a half (the equivalent of three and a half seasons of "Pretty Little Liars") trying to discover what happened to Alison and unmask the person known only as A. With so much going on, it's easy to lose track of who did what and when. Luckily, Alison's murder mystery is solved well before the ending of "Pretty Little Liars." Here's what actually happened.

Season 2, Episode 13 of "Pretty Little Liars," called "The First Secret," is where viewers learn what was motivating Alison around the time of her death, as well as some of the secrets she was keeping from her friends. In the episode, we learn that Alison was A's first victim; she received messages and texts from A well before any of the others. Between this and the tiny bits of story that the liars continue to discover thanks to old notes, old videos, and some of the people Alison knew before her disappearance, it becomes clear that Alison was making a concerted effort to discover A's identity before she disappeared. As we now know, A was actually the unpopular and bitter student Mona Vanderwaal.

Mona, who was revealed to be A at the end of "Pretty Little Liars" Season 2, attempted to kill Alison the night of her sleepover with the other girls, but she accidentally hit someone else with a shovel. Alison is still injured by someone else, though, and is discovered by Mona, who tends to her at a nearby motel. Mona helps Alison flee Rosewood before someone tries to kill her again, with Alison entirely unaware that she had just given A exactly what she wanted. Alison then stayed on the run the entire time her friends and family thought she was kidnapped and then dead. It's a shock to the girls when they discover that their friend is still alive, but less so to any viewer who had been paying attention to the breadcrumbs from the beginning.

The short answer to this question is, of course, nobody! That said, at different times throughout the first three seasons, the liars concocted several different theories around Alison's murder. At first they believed the killer could be Ian, Melissa's on-again, off-again boyfriend (considered by many to be the worst relationship in "Pretty Little Liars") who took secret videos of the girls and flirted with both Spencer and Alison. They considered Melissa, who found out about Ian and Alison and was none too happy. They thought Alison's brother Jason (who was initially played by Parker Bagley but was replaced by Drew Van Acker, which really bothered some fans) could have hurt her in a rage, and they also considered the possibility that Ezra killed her after they found out that he'd met her before she died. At one point in Season 3, the girls almost find themselves convinced that Byron, Aria's father, killed Alison after she threatened to expose his affair.

Luckily for them, none of these theories were correct because Alison was never killed. Alison's estranged sibling Charlotte accidentally hit her in the back of the head with a shovel after mistaking her for another girl wearing the same clothes. Their mother, upon witnessing this, tried to protect Charlotte by burying Alison, not realizing she was still alive. Alison was rescued by a seer named Mrs. Grunwald and left town in secret with help from Mona, who she didn't know was actually A.

Alison had a sibling named Charlotte who was named Charles at birth but later transitioned from her assigned gender of male to female. Alison's father demanded Charlotte be kept away from the rest of the family and held in Radley Sanitarium, but her mother loved her all the same and often brought her duplicates of the same clothes and gifts that she got for Alison. Charlotte's friend at Radley, Bethany, chose to borrow one of her outfits and follow Charlotte out the night Alison went missing. Unfortunately, the outfit Bethany borrowed looked exactly like what Alison was wearing that night.

Because Alison and Bethany were wearing the same outfit and looked similar enough to appear to be the same person under cover of night, Charlotte accidentally hit Alison over the head with a rock, believing her to be Bethany. Ironically, Charlotte did this because Bethany was hoping to harm Alison that night. Alison survived her blow to the head, but Bethany was also attacked that night by Mona, who mistook her for Alison. Mona hit Bethany in the back of the head with a shovel and left her for dead. Melissa found the unconscious body and, believing that it was Spencer who had hit her, murdered Bethany by burying her alive; all the while believing that Bethany was Alison.

Alison's lying is her worst quality in "Pretty Little Liars" and the same can be said for Alison the book character. Aside from that, the two versions of the character aren't very similar. In the books, Alison has an identical twin sister named Courtney, and their dynamic is actually the catalyst for all of the upheaval in the story. Alison convinces her parents that Courtney is crazy and gets her sent to Radley Sanitarium. A few years later, Alison visits Courtney and Courtney takes Alison's place. It is Courtney who makes friends with Aria, Spencer, Emily, and Hanna (whose relationship with Caleb is seen by many as the best relationship in "Pretty Little Liars"), and it is Alison who escapes Radley and murders Courtney. 

Mona is still the first iteration of A in the books, but she doesn't last too long: Alison kills her after stealing her identity as A. In the books, Alison is the main, endgame antagonist of the entire series. In the television show, A's identity switches around a fair bit and Alison eventually becomes reintegrated into her friend group — she even marries Emily and adopts twin daughters with her. The Alison of the show seems to be an amalgamation of Courtney and the least heinous parts of the book version of Alison. Whether or not this divergence was the best story decision comes down to personal opinion, though many fans have lamented the fact that book Alison was never brought to the screen. "Alison could have EASILY fallen into one of the MOST iconic TV antagonists of all time," wrote Redditor u/Kirbo300. "Imagine the legacy that would have left!"