  In this article we shall outline a derivation of the analogue of discrete
torsion for the M-theory three-form potential. We find that some of the
differences between orbifold group actions on the C field are classified by
H^3(G, U(1)). We also compute the phases that the low-energy effective action
of a membrane on T^3 would see in the analogue of a twisted sector, and note
that they are invariant under the obvious SL(3,Z) action.
