“Hey.” With that one word, uttered in the dead of night, young Charlie's life veers down a dark and unbelievable road. Some thirty years later, Dr. Charles Barry teaches physics at a small California college. Only in dreams do those childhood events reach him: the strange presence in the house, the otherworldly visits and the shadow over his beloved older sister, Megan, whose troubled inward life he could only glimpse. That is, until his father dies, and Megan, now an artistic wanderer, comes back into his life. With her come memories of unearthly creatures, a predatory entity and a harrowing trek behind the walls of the known cosmos, in order to save the very essence of his sister. Now, caught once more by the same forces, Charles returns to those places in the hopes of setting certain things right—and to keep Megan from slipping away forever.