Santo Innis is developing a revolutionary engine to counter the effects of high-pressure steam. His backer is Richard Vaughan, heir to Frederick Tregarron, owner of the Gillyvean estate. His world is turned upside down by the unexpected arrival at Gillyvean of Melanie Treggaron, Frederick's illegitimate youngest daughter. Desperate to prove the viability of his invention, Santo persuades Richard to let him fit one at Gillyvean's brewhouse. But when Bronnen Jewell arrives to brew the harvest beer she's horrified, fearing her loss of income on which she depends. As the lives of these four become entwined all four face the future with fear and trepidation.