In this novelization of a playscript, the formula for a powerful explosive is stolen. Locking his guests in the library, Sir Claud switches off the lights to le... » 

In this novelization of a playscript, the formula for a powerful explosive is stolen. Locking his guests in the library, Sir Claud switches off the lights to let the thief replace it, no questions asked. When the lights come on, he is dead. Hercule Poirot has to prevent a global catastrophe. «