Gilbert House: (the Temple of the Blind #2) by Brian Harmon
One year after Albert and Brandy discovered a fantastic labyrinth hidden deep beneath the streets of Briar Hills, Missouri, strange telephone messages begin stirring up memories of those dark passages. It seems that it may be time for them to return to that perilous world to finish what they started. However, when a strange envelope finds its way into his hands, Albert realizes that their destination this time is not the university's steam tunnels, where they began their last journey, but the bizarre ruins of an old men's dormitory in the woods north of the campus. But even with Wayne and Nicole at their sides, they are not prepared for the terrifying secrets hidden beneath the cellar door of Gilbert House.