Marco's millions
William Sleator
 It is about a boy named Marco who likes to travel. He often secretly rides buses far from home, though only his telepathic sister finds out. One day, his sister sees strange lights in the basement, and she and Marco investigate. They find a portal into another dimension, and thus the adventure begins. Marco finds strange insect-like creatures there, who are convinced that Marco/Lilly can save their dimension (and as a result save Earth) from their god, which is a naked singularity. But at what cost?