  We provide a complete solution of closed strings propagating in Nappi-Witten
space. Based on the analysis of geodesics we construct the coherent
wavefunctions which approximate as closely as possible the classical
trajectories. We then present a new free field realization of the current
algebra using the gamma, beta ghost system. Finally we construct the quantum
vertex operators, for the tachyon, by representing the wavefunctions in terms
of the free fields. This allows us to compute the three- and four-point
amplitudes, and propose the general result for N-point tachyon scattering
amplitude.
