The theory of supergravity on manifolds with boundary leads to very tightly constrained boundary conditions. When applied to low energy heterotic M theory, these boundary conditions are inconsistent with the work of Horava and Witten, but lead to a simplification of their action. The reduction of the new theory throws up some interesting new insights into gaugino condensation and no-scale supergravity models. The new theory also suggests the existence of a new type of index theorem.