Summer, 1796. After years of poverty, Mary Frith has come into an unexpected and rather large fortune. Her friends are sure she must be delighted with her new life, but Mary has an adventurous spirit, and the balls, dresses and endless rounds of tea aren't enough to keep her occupied for long. So when a mysterious spymaster asks her to keep a close eye on her friend Susannah ? and more particularly on Susannah's elegant but enigmatic husband ? Mary leaps at the chance, not realising the danger she faces. And with talk of rebellion in the military, it may be that England itself is under threat...In THE BLACKSTONE KEY we were introduced to an irresistible new heroine. Hugely entertaining, brilliantly researched and with a deeply satisfying mystery at its heart, THE COUNTERFEIT GUEST will enthral fans and new readers alike.