Season 2 Episode 10 (Aired: December 10th, 2009 on FOX)
Another piece of the pattern falls into place when we learn why Walter hasn't been able to remember how he opened the doors between universes.
A patient at a mental hospital has the back of his skull removed and something taken from his brain. Because the invaders are disturbed, their leader apologizes to the man for having to leave him behind like that before the group takes off. Strangely and unexplicably, Mr. Slater () is returned to health by this unorthodox procedure.
On the hospital's survaillance video FBI agent Olivia Dunham () recognizes the face of Thomas Jerome Newton (), better known as the frozen head the soldiers from the other universe were after in Momentum Deferred. He is the one William Bell (Leonard Nimoy) warned will open the doors between universes and thus cause the destruction of one of them.
Walter Bishop (John Noble), resident mad scientist for the Fringe devision and very uncomfortable with visiting mental institutions after being locked up in one for years, comes to the conclusion that Slater hadn't been mentally ill from the beginning. From own experience Walter knows that there are no miracle cures for mental illnesses and that getting better is long and thorny road. They find two more cases like Slater's and all have been referred to the hospitals by a Dr. Paris with mild symptoms that took a dramatic turn to the worse in a relatively short time. A search for Dr. Paris for questioning turns up blanks.
Olivia experiences a bout of depression because she feels all alone in her fight to keep the worst case scenario from happening. For the first time in her career she can't grasp what motivates the perpetrators.
Walter, upon studying the patients charts, finds something odd about their medication. All three were on anti-rejection drugs that have no efffects on mental illnesses but are given to patients who received organ transplants. Except, Walter concludes, they had foreign brain matter transplanted into their heads to keep it alive. Then the medication would make perfect sense.
Further investigation turns up unsettling news for Walter. He's been visited six times by Dr. Praris while at the mental hospital. Visits he can't remember. A look at his head confirms their suspicion. Walter has the same kind of scar the others have, only older and a bit differently shaped. A scan shows that unlike the others he had brain matter removed from him from an area that stores information. Walter once opened the doors between universes but hasn't been able to remember how since then. It looks like they literally found a trail to pieces of his missing memories.
To make sense the three pieces have to be implanted into a brain that can interpret the information stored in them. So Newton abducts Walter to hook him up with his memories. Time is of the essence, since brain matter can't survive long outside a human body. From Newton we learn that his universe is suffering from a blight that kills plant life. There are no trees or grass where he comes from. He tries to coax Walter into cooperation by threatening to reveal the reason behind Walter's original visit to the other side. Surely he doesn't want to loose his son Peter (), who died as a child in this world and who he stole from the parallel universe, a second time.
Olivia and Peter manage to locate Walter and Olivia gives chase to Newton and his compatriots, who she kills. Newton has his escape planned, though. He injected Walter with a poison and he's willing to tell Olivia on the phone where the antidote is if she lets him go. She hands over her cell and races back to the place where she left Walter and Peter to receive instructions on Peter's phone. Walter is saved in the nick of time, but the three pieces of brain matter are dead in their containers.
Walter is subjected to another scan when all is over and there we learn the identity of Dr. Paris who in reality is William Bell and that Walter gave up his memories willingly to be placed where only Bell could find them.
Review and clip from New York Entertainment:
We also got what we’ve been told is our last glimpse of Leonard Nimoy as the brilliant William Bell. Unfortunately, it wasn’t much of a cameo — he showed up at the conclusion so that we could learn that he was the mysterious doctor who placed Walter’s brain tissue in those other patients so that Walter would never attempt to walk through the doorway again. If that’s really the end of Bell on Fringe, you have to wonder how the writers will explain his permanent departure.