The Covenant have invaded Earth, in search of an ancient relic called the Key of Osanalan! They have taken thousands of prisoners including an unlikely pair: Ruwan, a hotel concierge, and Myras Tyla, a famous styllight player. Meanwhile, the Master Chief, Spartan-117, has stowed on board the Forerunner Dreadnaught and is also bound for Earth. Does one of these know the secret of the Key?