Agatha Christie's Partners in Crime: N or M? - Part Three

SINOPSIS

Part three of three. Tommy is held captive by the mysterious `N' along with Gilbert Worthing, who reveals that he has hidden a vital key that operates the stolen nuclear bomb. Tuppence comes to the rescue, and together they set out to retrieve the key - but it is hidden in the Sans Souci, where the enemy agent is lying in wait. The couple have to come up with an audacious plan to avert disaster. Last in the series.