The Cuckoo Sister sustains intrigue by a variety of techniques. Alcock's effective use of flashback is obvious at the outset. The reader is quickly drawn into the mystery by Kate's opening recollections of having been a shocked five-year-old who discovers she has a missing older sister. The flashback technique is used again to bring the novel to a satisfying conclusion, as the reader finally learns the truth about Rosie.

Alcock also conveys immediacy and credibility by using Kate's personal voice, rather than authorial, third-person narration. Kate's tight storytelling sustains continuity, heightens the emotional tension in the plot, and reinforces the theme of self-knowledge and growth. While the writing is serious and suspenseful, the reader is not overburdened because Alcock injects touches of humor or witty self-analysis to lighten the tone.

The characters are interesting and well-differentiated, from sensible Miss Wait to shallow Mrs. Seton, from streetwise...