When Douglas B. Douglas - leading light of the London theatre - premiers his new musical extravaganza, Blue Music, he is sure the packed house will be dazzled by the performance. What he couldn't predict is the death of his star Brandon Baker, on stage in the middle of Act 2. Soon another member of the cast is found dead, and it seems to be a straightforward case of murder followed by suicide. Inspector Wilson of Scotland Yard - who happens to be among the audience - soon discovers otherwise. Together with Derek, his journalist son, Wilson takes charge of proceedings in his own inimitable way.