It's a story about a physics professor who is investigating a device that creates planar force-fields. In its first run, an explosion destroys the device and the physicist is trying to obtain an answer to a seeming engineering problem using a second version. The story then goes on to describe how he gets trapped in the 2-D field and how a geometric property of the field, coupled with the fact that the planar field actually takes the form of a mobius surface, enables him to escape. There is a brief description of the way a stick figure on a paper mobius strip reverses orientation on completing a circuit.