Charlotte Alton is an elegant socialite. But behind the locked doors of her sleek, high-security apartment in London's Docklands, she becomes Karla. Karla's the unseen figure who, for a commanding price, will cover a criminal's tracks. A perfectionist, she's only made one slip in her career: several years ago she revealed her face to a man named Simon Johanssen, an ex-special forces sniper turned killer-for-hire. Now, after a long absence, Johanssen has resurfaced with a job. The job is to take out an inmate inside an experimental prison colony.