Neutron resonant scattering in the epithermal regime provides a potential tool for studying molecular dynamics. The theory is established by expressing the scattering function in terms of the Fourier and Laplace transforms of correlation functions which relate to the different positions of two coherent scatterers at different times. The correlation between resonant and non-resonant scatterers is especially useful in solving the scattering "phase" problem and obtaining further dynamic information. The theory is applied to the dynamic study of polyhedron and macro molecules in the linear regime (harmonic).