Summons From a Stranger — Debra B. Diaz

Lindsey Sims is a little different from most of her school friends--she dislikes cell phones, doesn't want a boyfriend, and loves to read mysteries. When her parents go on a cruise and leave her with her older sister's best friend, Julie, she gets to accompany Julie in answering a cryptic summons that leads to a gloomy mansion, storms and lights going out, and an attempt at murder that eventually succeeds. Besides that, she becomes an unwitting matchmaker for Julie with a guy she'd just as soon have for herself--if only she were older!
This young adult novel is for all ages, from twelve to those who just wish they were twelve again...