All signs point to the strong probability that somewhere in Merrie Old England, someone, for some purpose unknown (but certainly criminal) is building himself an atom bomb!

Obviously, it's a situation that requires the immediate attention of the Avengers - John Steed and Tara King - and they promptly swing into action.

The two search everywhere for clues - from jewelers' shops to a gypsy encampment - at one point the elegant Steed even descends from his stately Bentley to career about the countryside all day on a bicycle!

Time is running out. Can the Avengers find this maniac before he or she blows up half of England?