When a meteorite falls near her campsite in the San Rafael Wilderness, troubled teen Leona Hewitt ventures down into the crater looking for a souvenir. What she discovers changes her life. Contained in the meteorite is a sticky, mucous-like fluid that bends light, cannot itself be seen, and seems to grow in the presence of living tissue. It’s drawn to her. But when a government team arrives in hazmat suits and cordons off the meteorite impact site, Leona questions her decision to take it home with her. For one thing, there are rumors of an extraterrestrial threat. For another, it has been speaking to her. It wants to be worn . . . stretched on like a second skin. It’s seeking out her weaknesses, exploiting her deepest fear—that the only boy she’s ever loved will unearth the vile secret in her past and see her as a monster. Now it promises salvation. It can make her invisible.

It has been three months since Leona Hewitt dumped the body of her crush’s younger sister in the woods, praying he would never find out who did it. It has been three hours since she led him back to her rotting corpse. And three minutes since she showed up in Leona’s bedroom, alive. The culprit is a living substance secreted by a meteorite that can make people invisible . . . and apparently bring them back from the dead too. But something is terribly wrong with the girl claiming to be Ashley Lacroix. She doesn’t sleep. Sometimes, when she thinks no one is listening, she talks to someone who isn’t there. She says her soul has been eaten. She says Leona must die. Now, evading an unseen enemy, Leona must dig up the startling truth behind Ashley’s death before an insidious creature claims its next victim. Only the truth may be more chilling than she ever could have imagined. And the next victim may be herself.

It’s called dark matter, a living substance secreted by a meteorite that can make people invisible. Sixteen-year-old Leona Hewitt has been wearing it for twelve hours. It should be every teen’s fantasy—unbeatable pranks, a front row seat in her crush’s bedroom, a place to lick her wounds all alone. And it is . . . it is. Until she can’t get it off. In an instant, the fantasy becomes a nightmare. She’s stuck like this, invisible. Scratching at it, burning it off, cutting her skin off with a knife—nothing works. Dark matter is eating her, consuming her body like a bacteriophage and leaving behind a ghost. But when she wakes up in her bedroom, seemingly back to normal—only to find the city outside abandoned and ghostly quiet, she realizes she’s been transported to an impossible parallel realm. Electronics barely function, food turns mealy and rotten, fire snuffs out in seconds . . . and the only signs of life are the clues to a strange riddle left behind by a dead girl.

The girl sobbing in 16-year-old Leona Hewitt’s bedroom has the same long dark hair as her, the same startled hazel eyes as her, the same stuck-up nose as her. She’s identical in every way . . . and she’s here to take Leona’s place. By a twist of fate, Leona has until midnight on Halloween to outsmart her evil double and steal back her shattered life—and her soul—or forever become a ghost. But all the clues point to a startling truth. To her horror, she’s learning the other Leona has more claim to her old life than she does—even to her boyfriend. Could it be that after all this time, everything she knows about herself is a lie?