Two strangers, a research microbiologist and a commuter-line driver, both once fired by ambition and now disillusioned, encounter each other at a major crossroads in their lives. In a mistaken attack, one becomes a hapless victim of the other's desperation. As Thames Valley Serious Crimes Squad, headed by Mike Yeadings, investigates the disappearance of one of the men, grim secrets of national importance emerge. Involvement spreads beyond the men's families to a mysterious immigrant couple with a tragic past. Suspicion falls on DS Zyczynski's journalist lover as he is drawn in to counter the threat to a young child's life.