Professor Mondrian Killroy was a brilliant and eccentric English academic. Adored by his students, for years he gave classes unlike any others. His lesson 21 made a particular impact on young minds. It was focussed exclusively on the genesis of Beethoven’s 9th Symphony. But Killroy has disappeared and only Martha, a favourite student of his, knows where he is. She wants to listen one last time to that extraordinary lesson 21.