  Many theories which unify gravity with the other known forces of nature
predict the existence of an intermediate-range ``fifth force'' similar to
gravity. Such a force could be manifest as a deviation from the gravitational
inverse-square law. Currently, at distances near $10^{-1}$m, the inverse-square
law is known to be correct to about one part per thousand. I present the design
of an experiment that will improve this limit by two orders of magnitude. This
is accomplished by constructing a torsion pendulum and source mass apparatus
that are particularly insensitive to Newtonian gravity and, simultaneously,
maximally sensitive to violations of the same.
