First broadcast 22nd May 1984.

Col. Barclay is found dead and his wife is arrested for the murder, but Holmes is convinced a missing door key will reveal the true killer.

Jeremy Brett ... Sherlock Holmes
David Burke ... Dr. John Watson
Norman Jones ... Henry Wood
Lisa Daniely ... Nancy Barclay
Denys Hawthorne ... James Barclay
Fiona Shaw ... Miss Morrison
Paul Chapman ... Major Murphy
Shelagh Stephenson ... Jane
Michael Lumsden ... Young Henry Wood
Catherine Rabett ... Young Nancy
James Wilby ... Young Barclay
Maggie Holland ... Mrs Fenning
Colin Campbell ... Private Bates
David Graham Jones ... Pianist