Deeper by Roderick Gordon 643 pages

This is a sequel to Tunnels and to tell the truth I can't remember if I got through the first book but I downloaded this and caught up with Will's saga which picks up immediately where volume one left off. Will, Chester, and Cal on a train taking them away from the Colony to the deeper underground wilds. The story moves back and forth from different characters points of view as they are sometimes split up and reunited. While they are in the deep, their mother moves back and forth from the Deep to Topsoil, a legendary hero until her capture by the Styx. They try to brainwash her into thinking that her son Will turned evil and was responsible for his uncle's death. The Styx are super evil -- there is a lot of graphic torture and death of beloved characters. Some "characters" are brought back to life lessening the horror first felt. The boys become hopeful that their archaeologist dad may still be alive. Some parallels to The Emerald Atlas, but this is more for young adults than a younger audience.