On December 1727 an intriguing play called Double Falshood; Or, The Distrest Lovers was presented for production by Lewis Theobald, who had it published in January 1728 after a successful run at the Theatre Royal, Drury Lane, London. The title page to the published version claims that the play was ‘Written Originally by W.SHAKESPEARE’.
Double Falsehood’s plot is a version of the story of Cardenio found in Cervantes’s Don Quixote (1605) as translated by Thomas Shelton, published in 1612 though in circulation earlier. Documentary records testify to the existence of a play, certainly performed in 1613, by John Fletcher and William Shakespeare, probably entitled The History of Cardenio and presumed to have been lost.
Well you can buy it now and decide for yourself if this is a genuine play. There will be much discussion about it now that some major scholars have decided to throw their weight behind it as being true.