Leonard is alone and rootless, returning to London after his father's death. He moves in with his distant brother William and his family, hoping to renew their friendship but learning to drop his expectations of brotherhood. William is a former lecturer and activist who now runs informal meetings with ex-students. He is defiantly unworldly and forever questioning.

When a young student follows William's arguments to a shocking conclusion, it appears William has already set his own fate in motion. Against a backdrop of tabloid frenzy, Leonard can only watch as William embraces the danger in the only way he knows how, which threatens to consume not only himself, but his entire family.