A Cry in the Night by Mary Higgins Clark

When Jenny MacPartland met dashing artist Erich Krueger, he seemed like the answer to her prayers. Handsome, good with her two daughters, he only wanted to whisk her away from her poverty-stricken life. But when she married him and moved to his ranch, jenny began to worry. Stumbling across old family secrets, Jenny finds the shocking truth that lies behind a string of deaths--and fears she and her children may be next.