This is a brilliantly performed piece of theatre. Emily Watson is as always perfect in her role, but it is the performance of Ben Chaplin upon which this masterpiece resides. His is a flawless performance. The tension and pace are excellent. I've also seen The Affair. This is equally good with a similar theme. Just a note as a spoiler if you are thinking of buying this show... the fact that the lead is a Geneticist has absolutely nothing to do with the story. She could have been any professional in London.