Charlotte Alton is an elegant socialite. But behind the locked doors of her sleek, high-security apartment in London's Docklands, she becomes Karla. She'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. Karla helped him disappear before deciding to retire her double life. Now, after a long absence, Johanssen has resurfaced with a job, and he needs Karla's help once again.