What does the butler barrymore fail to mention during inquest?

In the play "The Importance of Being Earnest" by Oscar Wilde, there is no character named "Butler Barrymore." You are likely thinking of the play "The Hound of the Baskervilles" by Sir Arthur Conan Doyle.

In "The Hound of the Baskervilles", Butler Barrymore fails to mention that he has been communicating with his brother, Selden, the escaped convict. This is a crucial detail that ultimately helps Sherlock Holmes solve the mystery of the hound.

He also fails to fully disclose the contents of the letter he received from his brother, which leads to suspicion regarding his involvement in the events.