<P> A knew that there was a very good chance Hanna would regain her memory . Hanna's best friend, Mona Vanderwaal, informs the girls that she has also received texts from A, drawing the five closer together in trying to figure out who their tormentor is . Mona subtly encourages Spencer's fears that her sister, Melissa, might be A as well as Alison's killer . During Hanna's recovery masquerade celebration, she suddenly regains her memory, revealing that Mona is A. However, she, Emily, and Aria can't do much about it, because Spencer and Mona are on their way to the police station . After Spencer is warned about Mona by text, she tries to escape Mona's car, but Mona catches on rather quickly and diverts to a path in a more remote area of Rosewood . She tells Spencer everything, from seeing Ali launch a firework into Toby Cavanaugh's garage and blind her friend Jenna, to finding Ali's diary of secrets among a pile of old DiLaurentis junk the St. Germains left at the curb, discovering the girls' secrets that only Ali knew . Her motivation was to get revenge for her friend's blindness, even though Jenna and Ali had planned together to launch the firework . Mona didn't know this and got a scar on her stomach from the ordeal . Mona also drops the bombshell that Ian Thomas killed Ali, due to Ali's last diary entry about giving him an ultimatum to break up with Melissa . She then offers Spencer to become A with her and tell Hanna that she must not be remembering correctly, but she refuses . The two fight at Floating Man's Quarry and Spencer accidentally pushes Mona, who falls and has her neck caught between rocks . </P> <Ul> <Li> Real identity: Alison DiLaurentis </Li> </Ul> <Li> Real identity: Alison DiLaurentis </Li> <P> As the girls move into the big red house they are shocked to receive messages from a new person claiming to be Alison . At first, they believe it's just a prank, especially since the first "A" got major news time . Then the girls believe it's Ian Thomas, who is the prime suspect of the investigation . Spencer is especially certain of this until finding Ian's body in the woods bordering her estate and the old DiLaurentis home . The girls all get a message from "A," saying "He had to go . - A". </P>

Who is all on the a team pretty little liars