Accomplished physicist Sir Claud Amory has constructed a workable formula for one of the most deadly weapons known to man – the atom bomb. Hercule Poirot, with the help of Captain Hastings and Inspector Japp, is called in after the formula is mysteriously stolen and Sir Claud is callously murdered. A superbly crafted whodunit with endless red herrings and subplots of infamous spies. One of Christie's most gripping country house murder mysteries.