Ian Thomas was friends with Jason DiLaurentis. He used to date Melissa, but secretly also dated Alison, in addition to kissing Spencer. After Melissa and Wren broke up, he and Melissa eloped. After finding out about Ian's obsession with video taping people in private situations, Spencer and her friends believe that Ian is Alison's killer after seeing a video of him and her together the night that she died. When trying to kill Spencer for knowing too much, he is killed by A, who later took his body and set up a fake suicide for him.

Pretty Little Liars Quotes

We made a pact Emily. A is finally dead and we were all ready to get back to our lives and now we're on Planet Alison.

Spencer

Spencer: Senior year is supposed to be best year of life, did you know that it?
Emily: Yeah, if you survive it.