A system and method for controlling the humidity of an indoor space is disclosed. The system features a desiccant wheel which rotates sequentially through a plurality of distinct process air streams in order to optimize desiccant moisture adsorption at the process side of the desiccant wheel. This moisture is then deposited on the regeneration side of the wheel upstream of a cooling coil, increasing the dew point of the air entering the coil. The latent capacity and operational temperature of the coiling coil will be increased as a result, thus enhancing the dehumidification performance of the cooling coil and the overall efficiency of the system.