Quadrail series refers to a series of five (as of 2012) science fiction novels by Hugo Award winning author Timothy Zahn.In a space opera setting, human Frank Compton is hired by the Spiders, servant beings who operate the intergalactic Quadrail network, and their enigmatic masters the Chahwyn, to investigate a group-mind, the Modhri, which infiltrates other sentient beings and controls them either directly, or by subconscious suggestion.