Near-Infrared and Optical Spectroscopy of FSC 10214+4724

New infrared and optical spectroscopic observations, obtained with the W. M. Keck Telescope, are reported for the highly luminous infrared source FSC 10214+4724. The rest frame optical spectrum shows new emission lines of [Ne III], [Ne v], [O I], [O II], [S II], and He^+^, while the rest frame ultraviolet spectrum shows new lines of O IV] + Si IV, N III, N IV], Si ii, Ne IV, and possibly N II and [Ne III], as well as clearly showing that Lyα is self absorbed. The emission-line spectrum is most characteristic of a Seyfert 2 nucleus. The preponderance of spectroscopic evidence strengthens the case for a dust-enshrouded AGN powering much or most of the observed luminosity. The various spectral lines lead to a wide range in the inferred reddening and ionization parameter for this system, suggesting that we are viewing several environments through differing extinctions.