An indirect troffer. Embodiments of the present invention provide a troffer-style fixture that is particularly well-suited for use with solid state light sources, such as LEDs. The troffer comprises a light engine unit that is surrounded on its perimeter by a reflective pan. A back reflector defines a reflective interior surface of the light engine. To facilitate thermal dissipation, a heat sink is disposed proximate to the back reflector. A portion of the heat sink is exposed to the ambient room environment while another portion functions as a mount surface for the light sources that faces the back reflector. One or more light sources disposed along the heat sink mount surface emit light into an interior cavity where it can be mixed and/or shaped prior to emission. In some embodiments, one or more lens plates extend from the heat sink out to the back reflector.