On a dull Friday afternoon, in a smart flat somewhere in London, the German art critic David Keller (Jeroen Krabbé), morose and slightly drunk, receives a mysterious phone call from a man claiming to be an old acquaintance. Intrigued, David calls back later that day from a public phone, to discover that “Manfred,” a fellow political activist from ‘68, needs David's assistance in a political assassination. A Chilean military doctor and former torturer, Adolfo Vargas, is visiting London for a conference, and his death is meant to protest against the reprieves recently given to known torturers in Argentina and Chile. David is too taken aback to refuse. Books, pamphlets, and documents about Chile under Pinochet arrive at his publisher's which stir and trouble his conscience.

A week later, he meets his ex-lover Catherine (Susannah York) for dinner who, for reasons of her own, encourages him to take up again his project of writing a novel. She even offers him the use of her banker husband's farmhouse in Tuscany and an allowance. His publisher, too, supports the idea (“as long as it's not a fat best seller”), and David calls “Manfred” to receive details of Vargas’ intended movements.

On the third Friday, “Manfred” (Ulrich Wildgruber) turns up in London and accosts David outside the ICA. He tells him the assassination is off because Vargas, to save his skin, is prepared to expose details of US involvement and is therefore more valuable to the cause if left alive, especially since he will probably be eliminated by the people he has betrayed. David seems relieved. He meets Catherine at Harrods’ and later that evening is driven back to his flat by Catherine's teenage daughter, an anti-vivisectionist, who asks him what he thinks of direct action. David replies that he used to support “violence against property” but now believes it only achieves the opposite aim.

The next morning, he is awoken by a call from Sarah Yelin, the widow of one of Vargas’ victims and Manfred's Chilean contact. After hearing that the plan was to be abandoned, she had flown to London and now demands to see David.