to witness. >> narrator: but for people with parkinson's, the hope engendered by stories like peter sauer's proved short-lived. a year after peter's procedure, a series of fetal transplants at the university of colorado, utilizing a different surgical technique than the halifax team, yielded deeply disappointing results. while some recipients showed modest improvement, others wound up far worse, unable to even control their own bodies. >> even though some patients recovered, some patients recovered too much. in other words, they started to show excessive movements rather than just enough. so instead of being helped, they were actually made worse. >> narrator: it was a demoralizing setback, and, despite the halifax success, served to largely freeze the field of fetal transplants in its place. >> there's an old saying in science that research is the process of going up alleys to see if they're blind. and more often than not, they are. but that's what we do. >> narrator: meanwhile, the clock ticks. this year, some 50,000 people in the united states will wake up and sense something's wrong. the