A hypnotist is performing in a bar in front of an audience and the show is not going well. The hypnotist has not been able to hypnotise anyone for three months since he ran over a girl. Although it was not his fault, she died. For the past three months, the girl's father has visited the scene of the accident every day. There is a tree. In the tree he recognises his daughter and his daughter lives on in this tree. It sounds crazy, and it is. Tonight, the father sits in the audience. He doesn't want to scream and shout as he is still in mourning. He is hopeful that the hypnotist can somehow help him. »An Oak Tree« is a play about loss and liberation, about transformation and the power of suggestion. You are the audience of the hypnosis show but you don't have to join in if you don't want to! In every performance, the father is played by a new actor who has no knowledge of text. Nothing is improvised, and yet everything is always new. Everything goes awry, and yet the transformation succeeds right in front of your eyes.