Here he kept his wife imprisoned in her room while he, disguised in a beard, followed Dr.Mortimer to Baker Street and afterwards to the station and to the Northumberland Hotel.

His wife had some inkling of his plans; but she had such a fear of her husband--a fear founded upon brutal ill-treatment--that she dare not write to warn the man whom she knew to be in danger.

If the letter should fall into Stapleton's hands her own life would not be safe.

Eventually, as we know, she adopted the expedient of cutting out the words which would form the message, and addressing the letter in a disguised hand.

It reached the baronet, and gave him the first warning of his danger.
"It was very essential for Stapleton to get some article of Sir Henry's attire so that, in case he was driven to use the dog, he might always have the means of setting him upon his track.