The Manhattan Hunt Club — John Saul

Falsely convicted of a brutal crime, college student Jeff Converse sees his future vanishing before his eyes. But someone has other plans for Jeff, in a place far deadlier than any penitentiary. Jeff finds himself beneath the teeming streets of Manhattan, in a hidden landscape of twisting tunnels and forgotten subterranean chambers. Here, an invisible population of the homeless, the desperate, and the mad has carved out its own shadow society. But they are not alone. For someone has made this forsaken civilization a private killing ground. Now, with no weapon but his wits, and an unimaginable threat lurking around every dark corner, Jeff must somehow move heaven and earth to escape from a living hell....