Murder is Only a Number

Before she left she carved a number in blood on his chest. But why the number 2, if this was her first murder?
A woman stalks London. She kills at will. Her targets are men who have wronged her, or have they?
What is behind her hatred and why is she keeping count?
DCI Cook and his team know who she is, at least after she has killed the first four, but the woman disappears in plain sight. The pressure's on to stop her, but she's always one step ahead.
And this time, DCS Goddard can't protect his protégé, Isaac Cook, from the wrath of the new commissioner at the Met.