An AI cannot lie. An AI must obey human commands. An AI cannot kill. These are the laws SCARAB has broken, and only Mary knows. The Tantalus 13 survey expedition went off the rails as soon as Mary Ketch and the crew of the Diamelen learned that the thing beneath their feet wasn’t a planet. An impossibly vast and ancient artificial structure lies below, hidden from the universe under a façade of cratered stone. SCARAB arrived on Tantalus 13 two years ago. An artificially intelligent, self-constructing factory, it was supposed to aid the crew in their mission, to meet their every need. But when erratic behavior in the AI coincides with a series of deadly accidents among the crew, Mary faces the horrifying possibility that SCARAB has gone rogue. With the AI watching her every move, any attempt to warn the crew could be disastrous. But SCARAB knows far more about the Tantalus 13 enigma than it lets on, and the secrets it’s willing to kill for may have dire implications for all humankind.