Twins Gabriella and Daniella Canneziano appear rather inexplicably at the Desert Moon, an isolated ranch in the Nevada highlands. They are the guests of their uncle, the Desert Moon’s owner Sam Stanley, although they’re not really related — they’re the children from the second marriage of Sam’s ex-wife. He hasn’t seen them since they were very young and doesn’t know why they’re here now, except that their mother has been dead for a decade and their father has recently been sent to prison. Sam’s not the type to pry, though. Also at the ranch are Mary, who’s been the cook for 25 years; Chad and Hubert, who are nebulously employed charity cases; and Mrs. Ricker. Mrs. Ricker cares for Martha, who’s severely retarded. Martha and John are Sam’s adopted, adult children.
John and Danny very quickly fall in love and are engaged to be married. Mary is suspicious of the Cannezianos and spies on them, discovering that they are searching the ranch for something, something that will get them revenge on someone. Chad and Hubert both fall for Gaby. Mary overhears Mrs. Ricker threaten to kill both Hubert and Gaby if he doesn’t stop perusing her. Martha, who’s been known to be violent at times, has a crush on Chad and is intensely jealous of Gaby.
Two months into their stay, Gaby is murdered on the attic stairs and Chad shoots himself immediately after she’s discovered. Not long after, Martha dies of an apparent overdose of sleeping pills. Crime analyst Lynn MacDonald is called in to find the murderer.
This is very much in the Rinehart had-I-but-known school of mystery, much more so than the other Strahan books I’ve read. There are two components to the solution, both of which I identified and solved before the reveal, namely who are Martha’s biological parents and which of the Canneziano twins is which. Everything else hinges on that.