After a bomb goes off in the CI5 building and an operative is killed, Cowley gets a sinister phone call to say there will be more deaths, which there are, including an attempt to murder Bodie. Through an informant a man named Wakeman is incriminated - but Cowley swears that he killed him years earlier. Clearly an old associate of Wakeman is out for revenge, leading Cowley and the boys to a caravan primed with explosives.