Preston, 1741. The drowning of drunken publican Antony Egan is no surprise - even if it comes as unpleasant shock to coroner Titus Cragg, whose wife is the old man's niece. But he does his duty to the letter, and the inquest's verdict is accidental death.

But Cragg's close friend Luke Fidelis finds evidence to cast doubt on the events leading up to Egan's demise. Soon, suspicions are roused still further when a well-to-do farmer collapses and it appears he was in town on political business. Is there a conspiracy afoot? With the help of Fidelis's scientific ingenuity he sets about bringing the true criminals to light...