Dr. Watson is shocked to learn that his good friend Sherlock Holmes has a brother, Mycroft, and that they are on their way to meet him on an urgent matter. There they learn of the strange case of Mr. Melas, a Greek interpreter, who was roused from his sleep in the middle of the night and required to interpret for a man who was clearly being held against his will. That man was beaten, bound and not allowed to speak but only to write out his answers to the questions he was posed. Clearly his captors are trying to force him to sign a document and are also keeping his sister captive. When Melas is taken a second time to interpret, Holmes, Mycroft and Watson must move quickly if they are to prevent a murder.