Throughout history, we have always witnessed two extremes of theater. Abstract formalism and disregard for the fact that the play is the foundation of a theater. The other extreme is to find everything in the play and turn the theatrical work into something that is just a slogan and devoid of any aesthetics in line with the contemporary era of the work. Iranian theater is no exception to this issue. Meanwhile, genre plays are ignored by both sides. Because plays of this kind are accused of conservatism by both groups; by the first group, accused of conservatism in form, and by the other group, accused of conservatism in thought and content. Because the idea that genre as part of popular culture is ideological and conservative has been necessary for dominant social groups to define their taste as superior taste, and by this argument, maintain their cultural superiority over other groups. But we must take a closer look at these plays to understand what positive formal and thematic achievements they can have for the theater. Meanwhile, Anthony Shaffer is known as one of the most important playwrights in the genre field with plays such as “The Sleuth”, which have also been adapted into two films. The play “Whodunnit” is one of his plays, which is a complex work. But there is still a risk that this work will be seen as a play that ties their hands in performance, both from the perspective of directors who want to be authors, and from the perspective of directors who rely only on the play, it will be accused of being excessively complex in form and, as a result, devoid of content and thought. However, the theatrical achievements of this play are not few. Therefore, the present study aims to examine the textual and performance values of this play by addressing the theatrical achievements of this play, which falls into the category of metatheater, and in this regard, it also uses the theories of Lionel Abel.