Jack the Ripper is often called the world's most notorious unidentified killer, but he was not the first modern serial killer on the streets of London. Before him was another murderer who hunted from the River Thames – one arguably more sadistic and mercurial.

The Thames Torso Killer has always lurked in the Ripper's shadow, despite the fact he murdered and dismembered at least four people over two years. He started to kill in 1887, over a year before the Ripper, and his last murder was in 1889, almost ten months after the death of Mary Jane Kelly, the Ripper's last victim.

In Arm of Eve, Sarah Bax Horton conducts her own investigation and uses modern criminal profiling to come up with her own suspect – a known criminal who knew the Thames like the back of his hand.