When two elderly members of an exclusive club are suddenly found murdered, iconic pipe-smoking detective Sherlock Holmes (Basil Rathbone) and his ubiquitous sidekick, Watson (Nigel Bruce), are called in to investigate. The duo journey to a remote castle in Scotland, where the remaining five club members reside, and it is not long before another victim turns up dead. Holmes must use every ounce of his considerable intelligence to flush out the murderer before it's too late.