Two actor friends, Maggie and Julian (Eleanor Parker and Edward Mulhare), of Jessica's are due to appear in a revival of the play which launched their careers 30 years earlier, but Maggie finds threatening notes on stage, she stands down in favour of her understudy, who dies of cyanide poisoning. Jessica, as ever, decides to investigate.
Cyanide, theatre, stage actor getting threatening messages, an actress that would like to take the lime light and a detective who thinks he's Hercule Poriot - all this is classic murder mystery homage and done very well. There's some nice misdirection and some good humour from a detective who has illusions of being a golden age of mystery detective but gets it wrong. But Jessica gets it right.