He didn't do it - but who did?

A satisfying historical mystery set in Regency England, this book tells a story of Sebastian St. Gyr, a wealthy viscount, heir to an earldom, and a bitter, disillusioned man. Retired from the army after a few years of spying against Napoleon, Sebastian leads a life of a bored aristocrat, drinking, fighting duels, and seemingly not caring for his own safety. Until he is falsely accused of brutally murdering a young actress. Then he discovers that he does care whether he lives or dies. He cares a lot. Unwilling to perish for something he didn’t do, he sets out to discover the identity of the real killer.
To evade capture, he disappears into the seediest parts of London as he tries to piece together the victim’s last few days and find out who wanted her dead.
The novel is a bit grittier and darker than I like, but it’s written well, the pacing is relentless, and the characters come out of the pages almost alive. One of the aspects of this book is political. The timing is just before the Regency is announced, and the politicians and their parties are jockeying for power. The author doesn’t have any illusions about the politicians: they are all ruthless sociopaths. They don’t care whether St. Gyr is guilty or not. Some flimsy circumstantial evidence points to him – so of course the order comes down to the local magistrate to apprehend him and charge him. The masses must be appeased before the Regency starts. The justice – or the travesty of it – must be served.
It’s up to St. Gyr to clear his name, and he is practically alone. He has a few allies but none of them belongs to his family. For some reason, his sister hates him, and his father... well, that’s much more complicated. The author doesn’t describe St. Gyr’s family dynamics in details, and I was sorry for it. I wanted to know what happened to this family to make them all so cold and unloving, so hostile towards each other.