While on holiday, Peter and Debbie befriend Elsa: a lusty, Trump-loving widow from Denver, USA. She's less than woke but kind of wonderful. They agree to stay in touch – because no one ever really does, do they?

When Elsa invites herself to stay a few months later, they decide to look her up online. Too late, they learn the truth about Elsa Jean Krakowski. Deadly danger has just boarded a flight to London! But how do you protect all that you love from mortal peril without seeming, well, a bit impolite? Because guess who's coming... to murder!

The play takes a hilarious and satirical look at middle-class England's disastrous instinct always to appear nice.

Steven Moffat is the co-creater and co-writer of Sherlock and was head writer for Dr Who from 2010 to 2017.