Pure, heavenly escapism: The Unfriend, at the Criterion Theatre, reviewed

The Unfriend is a smart new family comedy which opens on the sunlit deck of a cruise ship. Peter and Debbie, a boring middle-class couple, are introduced to a clingy American tourist, Elsa, who worms her way into their affections. Before they know it, they’ve agreed to let her visit them at home after the cruise. A few weeks later, she shows up unannounced. By now the pair have learned from Google that Elsa is suspected of murdering her husband and several other members of her family. But they’re far too nice, and too English, to tell her to get lost. The crafty Elsa forms an alliance with their angry teenage kids, Rosie and Alex, and uses them to shield her from Peter and Debbie’s suspicions. It’s an amusing set-up and the script just about makes it credible all the way through.

Frances Barber plays the predatory Elsa as a brash, ageing sexpot, like Norma Desmond with a salty hint of Mrs Slocombe.