On the season 5 finale of Pretty Little Liars, we discover that Mona is not dead. She is actually alive. Hannah, Spencer, Aria and Emily are abducted and put into A’s “dollhouse.” They then find Mona wearing a blonde wig, wearing a mask and playing a piano. Mona then tells the girls that she is Alison, not Mona. She then pours the girls cups of tea as she acts strange and pretends not to know what’s going on. She also offers the girls cookies and insists that the girls not call her Mona. They must only call her Alison. Soon, a bell goes off and Mona exits the room, leading the girls to a room full of toys and a game called “Mystery Date Game.” Mona says that four chimes means it’s game time and their boyfriends are revealed in the game. Then, they receive “invitations” to prom. The girls try to convince Mona to escape with them, prompting an alarm to go off. Mona runs to her room and tells them that the alarm won’t stop until they’re in their rooms.
Later on in the night, Hanna’s door opens and Mona tells her they have three minutes to escape. Mona gives the girls info on possible ways to escape and lets them know that she’s only Alison when A is watching because that’s what it wants her to believe. The girls tell Mona about Alison’s murder conviction and then they all run back to their rooms.
The girls are forced to decorate for their “prom night” and Mona is made the head of the prom committee, as Alison of course. Meanwhile, she’s scheming with the girls to try to escape.