Alison Lauren "Ali" DiLaurentis is a fictional character in the Pretty Little Liars book series by Sara Shepard, and in the ABC Family television series adaption. She is portrayed by Sasha Pieterse in the television series. Throughout the first three seasons of the television series, Ali mostly appears in flash backs and hallucinations. The character of Ali plays a more prominent role in season 4. Alison has an alter ego named "Vivian Darkbloom" whom she uses to spy on "A." She is now in hiding from A while trying to help the Liars. Alison returns to Rosewood in Season 5, after the Liars believe Shana was "A". In the summer finale, it is revealed that Alison may have lured Bethany Young to Rosewood because she found out about an affair between Mrs. DiLaurentis and Mr. Young.