Mary's son was taken from her at birth which add the to the list of reasons of why she hated her sister. She found out that Charles was not dead and buried at her Aunt Carol's house but transitioned into Charlotte DiLaurentis.
In anger, she switched Jessica's blood pressure medication with Peter's. Her original medication was to raise her blood pressure while Peter's lowered his. After Jessica ingested the pills, her heart gave out and her body laid in her yard until it was discovered by Charlotte who came to say goodbye.
Mary later returned to bury Jessica in the backyard of the Hastings in order to frame Peter. Her body a day later was discover by the Liars and Jason.
In the closing scene, Jessica's dead body is seen being dragged across her yard. A then buries her body in a backyard.
With Alison DiLaurentis home and Jessica nowhere to be found, Kenneth DiLaurentis asks Ashley Marin to look into Jessica's emails to see if there is any indication of where she is. When Hanna looks, she finds an unsent email from Jessica to an unknown recipient saying "I can't protect you anymore". The Liars theorize that Jessica decided to go deliver this message to the recipient in person and that whoever it was killed her to protect themselves.
Later that night, Pepe starts barking at something in the Hastings' back yard. The Liars and Jason go out to find Jessica's hand sticking out of the ground. The police are called and Jessica's body is dug up and taken away, as Alison silently cries in the background.
Alison texts The Liars and tells them that an initial autopsy could not determine Jessica's cause of death and that, instead, a toxicology report was going to be done.
Spencer goes to see Alison, who informs Spencer that the toxicology report came back showing traces of Losartan in Jessica's system. Jessica had low blood pressure and took medication for it, whereas Losartan is for the opposite problem. This means that someone switched her medication, although it's unknown who did it, and Jessica's heart stopped working as a result.
At school, Alison receives a message from 'A' saying "I buried your mom the same way I watched her bury you", with an attached video of Jessica being buried. This suggests that whoever hit Alison with the rock that night is the same person who killed Jessica and the current 'A'.
A news report on TV shows that the police suspect Charles DiLaurentis of murdering Jessica.
Alison breaks into the Rosewood Police Department and finds a board with photos of Jessica's body on it linked to other unsolved murders.
In the Hastings' kitchen, the moms get drunk and discuss Jessica's murder. Veronica starts ranting that it wasn't bad enough that that Jessica tried to steal her husband, but then her "sicko son" had to bury her in the Hastings' backyard and that he's tried to frame her entire family. Pam brings up the possibility that Kenneth murdered Jessica for keeping their son a secret all those years. Veronica suggests that they go ask him themselves and they go to the DiLaurentis House, only to find Kenneth gone.
Charlotte DiLaurentis tells Alison that the night she escaped police custody, she snuck home to say goodbye to their mother. When she arrived, Jessica's body was laying outside the DiLaurentis house. Charlotte tearfully begged her mother not to leave her. She then dragged Jessica's body to the Hastings' back yard and buried her there. Charlotte seems unaware of who killed their mother.
Peter reveals that Mary switch Jessica's pills with her his own prescription which killed her and buried her in their backyard to implicate him for revenge.
- The identity of Jessica's killer is not revealed with the rest of the answers regarding 'A' in "Game Over, Charles ". This suggests that it is part of a larger mystery and will be answered in Season 7.
- At first it was believed that 'A' killed Jessica, but in "Game Over, Charles", Charlotte reveals that she found Jessica's body outside the DiLaurentis House after she escaped police custody.
- Her killer was revealed in "Power Play".