In the next "Fringe", a child music prodigy is abducted by a serial kidnapper. It is then discovered that a sequence of flashing lights appeared at the abduction, which Walter links back to his bunkmate at St. Claire's Hospital. Much to Peter's dismay, Olivia encourages a return visitation for Walter, and Walter's determination to help ends up having chilling ramifications.
The November 18 episode is called "The Equation". On this particular chapter, Olivia depicter, Anna Torv said, "I thought 'The Equation' was a really beautiful script. A little boy is abducted while on a drive with his father. His father stops to help this woman whose car's broken down and sees some lights and then all of sudden his son and the woman in the car have disappeared and he doesn't quite know what's going on and we find out that this same kind of story has been told before, but most of the people that have told it have inevitably gone mad or had quite frightening psychotic outbreaks."
She continued, "And Walter seems to remember an inmate in the asylum telling the same story and he was a genius mathematician. So Walter ends up going back into St. Claire's where he tries to get information from this old inmate of his, Dachsel. It's really great. I don't want to give too much away but it's some great stuff in 'The Equation.'"
"And then we find out that the car was registered to this woman who had died about ten years ago, and all the people that have been abducted were all kind of like geniuses in particular scientific fields, expect this little boy who was in fact a brilliant, brilliant piano player and the mathematics of music kind of come into play. I don't know. I don't want to say anything more, it's a really lovely, lovely episode."