The show will be at the Cambridge Arts Theatre until Saturday, September 27.

A menage-a-trios with a difference, Daytona, written by and starring Oliver Cotton, is set in 1986.

In a comfortable apartment in Brooklyn, an elderly Jewish couple are dancing. Elli (Maureen Lipman) and her husband Joe (on the opening night in Cambridge played by understudy Andrew McDonald) are rehearsing for the seniors' dance competition taking place the following night.

They argue lightly about what he is going to wear, what she is going to wear, and whether they will go out with friends to eat after the contest. They have 'cawfee'.

At 10pm that night, Joe's brother Billy (Oliver Cotton) turns up after 30 years. He has come back to tell Joe and Elli that he was on holiday at Daytona Beach when he recognised a Nazi guard from an extermination camp in Poland. He thought about it for five days but then looked him in the eye and shot him dead, in the swimming pool, in front of hundreds of people. The blood turned the water red.

Billy wants Joe to identify the Nazi so the world will understand why Billy did what he did. They had both witnessed the guard's daily brutality, his random shootings and beatings. Joe refuses. The deftly-written play then spirals round the merits of revenge. What is the difference between revenge and justice? What difference does it make to those who suffered and died so long ago?

It also emerges that the reason Billy disappeared three decades earlier is that he and Elli were in love. Two men – one girl. Someone had to leave.

He left without telling the other two. Elli was distraught. She was ill for two years.

“What we were doing wasn't good,” says Billy in his explanation to Elli 30 years on. “What's so right about good?” answers Elli.

This is a tour de force for Oliver Cotton who inhabits the jittery character of Billy who has not just left his brother and the love of his life - he has changed his name and thinks he has obliterated his past. But he buried it still alive. Shockingly confronted with it, he finds that after all he cannot let it go. He has never let it go.

Maureen Lipman as the woman who loved one man and couldn't bear to hurt another, is also a privilege to see, an actress who can give tragedy and humour the same warm, human touch so it always stays real.

Andrew McDonald (standing in for Harry Shearer, the voice of Mr Burns in The Simpsons) completes an ensemble cast. They create a world. You could see the three of them sitting down companionably to eat chicken soup. The play offers no surprises, the plot has no unforeseeable twists but the writing is fine, the performances are exemplary. It's an old-fashioned, gentle play with good speeches. It has a beginning, a middle and an end. It has an eternal theme and will stay in the mind.