Mia Lockhart has a secret. Her mother was a keeper, as was her grandmother — women who were warriors, healers and protectors. And when a mysterious man enters her life, she puts this to the test. Adrian Ashton is a brilliant scientist — and a killer. With the aid of an ancient Chinese text, he has mastered the art of capturing the chi of his opponents — the vital energy that flows through their bodies. Mia finds herself drawn to his dark genius. But when he targets the man with whom she is falling in love, she is forced to choose between them. Soon it becomes a fight to the death in which love is both the greatest weakness — and the greatest prize.

Gabriel Blackstone has an unusual talent. A computer hacker by trade, he is also able to enter the minds of others. But he uses his gift only reluctantly — until he is contacted by an ex-lover who begs him to find her step-son, last seen months earlier in the company of two sisters. And so Gabriel visits Monk House, a place where time seems to stand still, and where the rooms are dominated by the coded symbol of a cross and circle. As winter closes in, Gabriel becomes increasingly bewitched by the house, and by its owners, the beautiful and mysterious Monk sisters. But even as he falls in love, he knows that one of them is a deadly killer. But which one? And what is the secret they are so determined to protect?