This disappointing thriller from Dirty Harry director Don Siegel stars Michael Caine as an agent whose son is kidnapped by a mysterious military organisation which demands diamonds in return for his release. Like all good heroes from John Buchan's Richard Hannay onwards, Caine finds himself the number one suspect and thus spends as much time keeping out of the clutches of the law as he does tracking down the real culprits. The plot is over-thickened with cat-and-mouse sequences and Siegel's acclaimed naturalistic style is intrusive here, but the performances are fine, especially those of Donald Pleasence and the star of Last Year at Marienbad, Delphine Seyrig.

A British agent's son is kidnapped and held for a ransom of diamonds. The agent finds out that he can't even count on the people he thought were on his side to help him, so he decides to track down the kidnappers himself.