I'll Be Your Sweetheart - Joan Jonker

Not a day goes by without Molly Bennett and Nellie McDonough counting their blessings. But when an elderly neighbour, Flora Parker, is robbed of her most treasured possession, and left without a penny to her name, the two friends jump at the chance of setting their detecting skills in motion. Meanwhile, Molly's youngest daughter, Ruthie, and her best friend, Bella, are making plans for their joint sixteenth birthday party. Ruthie is determined to look glamorous, a real knock out, to catch the eye of a certain boy for whom she's got more than a soft spot.