The Fourth Protocol

“If the Fourth Protocol is ever breached, there would be no warning, just a nuclear explosion from a bedsitter... The unthinkable has just begun.”

A secret Soviet plan called Plan Aurora breaks an agreement no one was meant to touch, the Fourth Protocol. John Preston (Michael Caine), an MI5 agent, tries to trace it while a trained Soviet operative (Pierce Brosnan) settles into a quiet English country town and starts putting together a nuclear bomb. John Mackenzie keeps the two men on separate tracks, Preston among his files and Brosnan alone with the parts.