Later, Kristen's body was found in the pool. The letter opener, with Susan's fingerprints, was found...but Susan (who had unknowingly been drugged by Kristen) denied hurting her.
It was later revealed that Kristen was still alive...and impersonating Susan. She had had Susan sent to an island to be the prisoner of the "Turban Man". She filled Stefano in on what she'd done. In the meantime, Laura confessed to Kristen's murder.
Meanwhile, on the island, Susan began having flashbacks of the night of the murder. She remembered getting a mysterious phone call, and a woman named Penelope (who looked exactly like Kristen) knocking on her door. Penelope turned out to be Susan's sister. Together, they had come up with a plan to return to Salem and confront Kristen.
Celeste began to regain her memory from that night. She remembered seeing Laura shooting a gun...and being nicked by one of the bullets. She also remembered that Kristen was drunk, but had not been hurt. In addition, she remembered seeing a pair of gloved hands holding Kristen's head under the water. Laura was cleared of the murder.
Kristen, disguised as Susan, was shocked when Edmund confessed to her that HE had drowned Kristen.
On the island, Susan continued to have flashbacks. She remembered being on the plane and watching as Penelope had taken something to help calm her nerves (resulting from her fear of flying). She escaped from the "Turban Man" and returned to England. She was able to convince Edmund's mother, Violet, that she was the real Susan. She & Edmund were reunited and it was revealed that he had actually killed Penelope...not Kristen.
Susan forgave Edmund, and together they set Kristen up...and had her turned over to the "Turban Man"...where she still is today.