Open the Final Evidence

Marta believes she accidentally gave Harlan a fatal morphine overdose. In fact, Ransom had secretly swapped the contents of the vials beforehand, intending exactly that — but Marta, guided by instinct rather than the labels, gave Harlan the correct medicine. Harlan, convinced she had made the mistake, took his own life to protect her. Ransom later killed the housekeeper Fran when she tried to blackmail him. Benoit Blanc exposes him; Ransom lunges at Marta with a knife that turns out to be a retractable prop. Marta inherits the estate, and the final shot shows her on the balcony holding the "My house, my rules, my coffee" mug, looking down at the family.

The mysterious Cockney woman who sells Sir Wilfrid the incriminating letters is Christine herself in disguise. By discrediting her own testimony, she secures Leonard's acquittal. She then admits she knew he was guilty. Leonard reveals he plans to leave her for a younger woman; Christine stabs him with the knife from the evidence table. Sir Wilfrid, restored to vigour, announces he will defend her.

U.S. Marshal Teddy Daniels does not exist. He is Andrew Laeddis, a patient at Ashecliffe who killed his wife Dolores after she drowned their three children. The whole investigation is an elaborate role-play staged by Dr. Cawley as a last attempt to bring him back to reality before lobotomy. Andrew briefly accepts the truth, then appears to relapse. His final line — asking whether it would be worse to live as a monster or die as a good man — suggests he is choosing the procedure knowingly.

In the final (chronologically earliest) scenes, Teddy tells Leonard that he already killed the real John G. long ago and forgot, and that Teddy has been using him to kill others since. He also suggests that the story of Sammy Jankis may be Leonard's own — that Leonard's wife survived the attack and died from insulin he administered. Leonard, choosing a purpose over the truth, writes Teddy's licence plate as a fact to follow, ensuring he will hunt and kill Teddy — the murder we see at the film's start.

Amy staged her own disappearance to frame Nick for murder. After she is robbed while hiding, she turns to her ex-boyfriend Desi, then kills him and returns home claiming he abducted her. Nick knows the truth but cannot prove it. Amy reveals she is pregnant, having used Nick's stored sperm, and he stays in the marriage, both performing the perfect couple for the cameras.

There is no conclusive solution — the case remains officially unsolved. The film strongly points toward Arthur Leigh Allen. In its final scene, survivor Mike Mageau identifies Allen from a photo line-up. Closing title cards explain that Allen died in 1992 before he could be charged, and that later DNA tests did not match him, leaving the identification disputed.