One of three young-adult sisters, Shirley Mortimer still lives at home with her parents in London. Considered the plain and unaccomplished one in not having a job, she is always relegated to the background, more like a servant than a family member. Rather than go with her parents on holiday to the continent, Shirley decides--with help from her friend Marjory Fielding, the only one who knows her plans--to strike out on her own for independence. She plans to work as governess for her father's young criminal-lawyer friend David Trent, who requires someone to look after his adolescent son Derek. Beyond the independence, Shirley wants the job in her immediate attraction to David himself when she met him when he came to the Mortimer house for tea one afternoon. The one catch for Shirley is that David is looking for a middle-aged woman for the live-in job, not wanting to appear improprietous with a young woman, so Shirley dons a disguise and transforms into middle-aged governess Mrs. Halifax. The situation becomes more complex when she: meets artist Norman Harrington, whom David is defending in a high-profile murder trial, which feels personal because Norman's situation is all too familiar to David.
—Huggo