When Frankie Stein's older brother brings home a bit of biological material from the mysterious laboratory where their cold, cerebral father works on genetic engineering, she puts some of it on the windowsill with a drop of her own blood in lieu of a petrie dish. After a flash of lightning, ""Monnie"" (for monster) begins to grow rapidly--an evolving blob, with red eyes and an endearing smile, that soon needs to be rocked to sleep and later plays like a toddler. Meanwhile, Frankie has kept Monnie a secret from her family but enlisted the aid of new friends Julia and John Hobson (she suspects best friend Hazel will prove inadequate because ""I had chosen my friends. . .just because I liked them, not for use"") and the unintellectual but fatherly gardener, Alf. Alcock combines the sure appeal of a scientifically generated creature with serious themes of nurture and responsibility: ""'Whoever made the monster, I think it's God's creature now,' I said, hoping to shift some of the blame,"" Frankie reports early in the story; yet she and her friends do care for Monnie till the inevitable escape to a more suitable environment, each in accordance with a deftly defined personality (most notably Hazel, who turns out to be the best sort of friend); and this drama opens the way to believable, tentative communication between Dr. Stein and the daughter he really does love. Though the plot is not unique, the complex relationship among the characters and the intriguing ambiguity at the conclusion make this a story to attract a wide range of readers.