Holmes and Watson are asked by a masked nobleman to save one of the royal houses of Europe from ruin. This is the story of how a great scandal threatened to affect the kingdom of Bohemia, and how the best plans of Sherlock Holmes were beaten by a woman's wit, Miss Irene Alder.

Holmes and Watson unravel the mystery of the 'dancing men' and apprehend the man who has been threatening Mrs Cubitt. But will they be in time to prevent her attempted suicide and catch the killer behind Mr Cubitt's tragic murder?

Apart from the Minister himself, Percy Phelps is the only man in the Foreign Office with access to the secret treaty between Great Britain and Italy. When the treaty disappears Phelps, tortured by guilt, calls on the services of Sherlock Holmes. With world peace in danger, it seems only one man can help but can Holmes find the treaty in time?

Violet Smith consults Sherlock Holmes over the mysterious cyclist who has been following her on a regular basis. Meanwhile, the efforts of three men, returned from South Africa to defraud her of her inheritance by forcing her to marry one of them, are thwarted by Holmes and Watson. Is there a connection, who is the solitary cyclist and is he really trying to protect her?

Holmes and Watson visit Aldershot, to investigate the violent death of Colonel James Barclay. A tragic love story is unveiled which exposes the identity of a horribly deformed man, the 'crooked man'. His involvement in the case begins to place doubt in Holmes' mind - could Barclay have died of natural causes?

Holmes is approached by Helen Stoner, who feels threatened by her domineering step-father, Dr Grimesby Roylott. Her sister died mysteriously just before her planned wedding, and Helen has heard again the curious whistle she first heard on the night of her sister's death. Holmes perceives great danger and lays a complicated plan to defeat the threat to the beautiful Helen.