The Mariner's Secret, a Matt & Heather Thriller by Mary TomasiDubois

Thugs, chases through the streets of San Francisco, scientific discoveries, and other mysteries abound! Matt and Heather Townsend, orphaned when their bioscientist parents are killed in the 1989 Loma Prieta earthquake, become wards of their Great Aunt Estelle. Her stately old house in the Marina District holds intrigue, and a secret. Fortunately, Matt discovers the secret on his thirteenth birthday, and not too soon. He was about to go stark raving mad with boredom. Years earlier and unkeknownst to anyone, rumors of Jon and Josie Townsend's secret research had enticed SafGen's head of security to break into the head office in an attempt to steal the research papers. His goal was to sell the papers, confident that certain foreign regimes would pay handsomely for the exciting new discovery. Coming up empty-handed, he devises another plan to get his hands on the papers. Roger Hill, the subservient butler, fools everyone but Matt and Heather. Their only chance at protecting their aunt and governess, as well as themselves, is to use the house's secret.