The "mythology" of this series is becoming very dense; you have to pay close attention to, often simultaneous occurrences, one which furthers the mystery of colliding universes, and the other, a standalone mystery.
This episode was illustrative of this; Walter trying desperately to stop the widening vortex, and feeling that he is not capable, while offering assistance into a fringe mystery. The mystery involves an aeronautical engineer, experimenting with dense metals, to find a way for his crippled son to walk again. This was less interesting than the seemingly simple things Walter kept trying, in order to communicate with Bell. It was wonderful that in the end it was a simple ringing of "the bell", that brings back Bell's spirit. And once again it is the stalwart, Olivia, who has to transform, in the service of the Fringe division.
Please read the following before uploading
Do not upload anything which you do not own or are fully licensed to upload. The images should not contain any sexually explicit content, race hatred material or other offensive symbols or images. Remember: Abuse of the TV.com image system may result in you being banned from uploading images or from the entire site – so, play nice and respect the rules!