Four years ago, Caulborn agent Vincent Corinthos stopped a hellish ritual intended to transform Ulysses Pendleton into a creature of utter darkness. With Pendleton safely imprisoned in Ashgate Penitentiary, Vincent and the rest of the Caulborn figured the world was a little bit safer. Until now. A catastrophic failure with the prison's security systems sends Vincent and the rest of the Caulborn into Ashgate to try and prevent the inmates from escaping. They secure all but one. Pendleton. Now, Vincent's in a race against the clock to find Pendleton before he can finish the job he started four years ago, and smother Boston in shadows.