Sarah Leeson is the most interesting character in the book. A shy and weak character, she is haunted by her past and the responsibility placed on her by Mrs Treverton.When she reappears as Mrs Jazeph, Rosamund's temporary nurse, Collins carefully manages her behaviour to make it both creepy and suspicious, but also sympathetic. As her past is slowly revealed, all Collins' skills are deployed to ensure that what may be ostensible faults of character to a Victorian audience never come between Sarah, Rosamund and his readership.Rosamund is a sparkier heroine than the bland Mary Grice in Hide and Seek. She is headstrong and has a temper, and although she and her husband Leonard Frankland (who is blind for some reason, as it has little impact on the plot) are of such unimpeachable uprightness and morality that they restore Andrew Treverton's belief in humanity, she is also believable as she comes to terms about the unexpected change in her circumstances as the Secret is revealed.
The novel works on several levels. Collins handles the Secret with great skill, ensuring that the reader is intrigued from the first chapter, and then gradually building the tension through the interplay of the main characters as Rosamund firstly finds out about the Secret, then Sarah tries to hide it once again. It is also very carefully balanced in terms of characterisation. Any oversweetness on the part of Rosamund and Leonard is balanced by the misanthropic Andrew Treverton and his manservant Showl.The intensity of Sarah Leeson is balanced by her engagingly eccentric Uncle Joseph.And finally, it is morally engaged, subtly showing the iniquity of Victorian laws on marriage, illegitimacy and inheritance, perpetual themes of Collins. Compared to Collins' other early works, this is really the springboard to his masterpieces such as The Woman in White, as by now all the key elements are in place - the sensation, the drama, the pathos - for Collins to make his mark on the Victorian novel.