September 1799. William Pitt is attempting to force through anti-slavery legislation, but many have a vested interest in preventing this change and would go to dangerous lengths to stop it. Meanwhile, Tom Pascoe of the river police is grieving for the woman he loved and looking for solace at the bottom of a bottle. Tom's drinking has made him increasingly belligerent and unpredictable, so when he is called to investigate a body found in the Thames - that of an MP and a close associate of William Pitt - there's doubt whether he's up to the task. But Tom must pull himself together, or be dragged under; Pitt's life is in his hands.

In the dark and slimy streets of Wapping a prostitute is beaten half to death, a not uncommon fate in late 18th century London. So begins this gripping tale set in 1798 in the Port of London: a cruel villain holds sway over the underworld. His name is Boylin. His face is scarred by lime and his back by the two hundred lashes he received following a naval court martial. He holds Captain Tom Pascoe responsible for his suffering. They meet again when Pascoe becomes River Surveyor for the newly formed marine police. They've had orders to investigate a sudden fall in government revenue that is affecting the nation's ability to fight the war against Napoleon and stem the rising tide of Irish rebellion. Pascoe knows that Boylin is behind it, but he can't prove anything, yet. THE WATERMEN follows these two adversaries across London as they try to outwit one another. Working alongside Pascoe is Sam Hart, a Jewish immigrant with his own agenda, Pascoe throws the rule-book out the window, scouring East London and the docklands in search of information. But fate takes a cruel twist when the two men find themselves involved with the same woman - there's much more at stake than the fate of the nation.

River Surveyor Tom Pascoe of the Marine Police finds the bodies of two men entombed in the crew cabin of a sunken lugger. Suspicion falls on a third member of the crew seen fleeing the scene. He had a known motive for murder. Against the background of a nation at war with Napoleon, Tom Pascoe finds his own life under threat as he digs deeper into the case. He uncovers the existence of French agents whose task is to undermine England's ability to continue the war. Tom's job is further complicated by the presence of a new member of the police crew with a shocking secret of his own...