The marriage of Rupert and Sarah is on the rocks and their friends Charles and Madge, both of whom are lawyers, agree to handle the divorce. After the curtain has been up a few minutes, Rupert forgets his lines and threatens to kill Charles in full view of the audience because he's been having an affair off stage, with Rupert's real wife, Madge. The rest of the cast try to ignore the incident and forge ahead with the original play but Rupert picks up a knife and advances on Charles, who is forced to take cover in a large cabin trunk which is on the set at the time. A real life marital comedy now evolves. The situation is further complicated when the actor playing the old father, Edward, makes his entrance. He is an ageing Shakespearean star, once famous for his King Lear but now an alcoholic on the skids. He happens to have asked his new agent to the performance that night. Edward is blissfully unaware that the play has switched from art to life. Out of loyalty to a fellow actor, the rest of the cast do their best to accommodate the poor chap, but he gradually begins to crack up, especially as some of his cues are coming from a cabin trunk.