What is the 4 version of trilogy?

Excuse me, could you please clarify what you mean by "the 4 version of trilogy"? Are you referring to a specific literary work that has a fourth installment in a series of three books, or perhaps a film franchise that has added a fourth film to its original trilogy? Could you provide more context or details about the specific trilogy you're inquiring about? Without this information, it's difficult to give an accurate answer to your question.