The 1727 play is based on the "Cardenio" episode in "Don Quixote", and, more specifically, on Thomas Shelton's English translation of the first part of the novel which appeared in 1612.
The 1727 play is based on the "Cardenio" episode in "Don Quixote", which occurs in the first part of the novel. The author of the play appears to know the novel through Thomas Shelton's English translation, which appeared in 1612.