The Mariner's Secret (Book 1 in series - Matt & Heather Thriller)
by Mary Tomasi Dubois
Thugs, chases, scientific discoveries, and other mysteries abound!
Matt & Heather, orphaned when their bioscintist parents are killed in the 1989 earthquake, become wards of their great aunt Estelle. Her stately old house holds intrigue, and a secret.
Roger Hill, the subservient butler, fools everyone but Matt & Heather - their only chance at protecting everyone is to use the house's secret.