July, 1964. At home in Kent Winston Churchill wakes to a visitor: someone he hasn't seen for a while, a dark, mute bulk, watching him. It's Mr Chartwell.

In Battersea, Esther Hammerhans, young, vulnerable and alone, answers the door to her new lodger. Through the glass she sees a vast silhouette. It's Mr Chartwell.

Mr Chartwell is a large, black dog.

He is charismatic and dangerously seductive, but as their lives are slowly drawn together, can Esther and Winston withstand his strange, powerful charms and strong hold? For Mr Chartwell's motives are far darker and deeper than they seem.