When a fissure explosively opens in an English mud flat during a military exercise there, injuring one soldier and killing another, an American research scientist at a nearby nuclear plant joins with a British investigator to discover why the victims were radioactively burned and why, shortly thereafter, a series of radiation-related incidents are occurring in an ever-growing straight line away from the fissure.
Elenco: Dean Jagger , Leo McKern , William Lucas , Edward Chapman , John Harvey , Michael Ripper , Anthony Newley , Ian MacNaughton , Peter Hammond , Kenneth Cope , Michael Brooke , Frazer Hines , Neil Wilson , Stella Kimball , Jameson Clark , Jane Aird , Neil Hallett , Marianne Brauns , Max Brimmell , Brown Derby , Norman Macowan , Anthony Sagar , Edwin Richfield , John Stone , Lawrence James , Frank Taylor , John Stirling , Jack Lambert , Archie Duncan .