Geoffrey Homes is the pen name of Daniel Mainwaring, novelist and screenwriter. He is best known for Eleven mi horca (Build My Gallows High) and its film adaptation, made by Mainwaring himself, Retorno al pasado (Out of the Past).

Then There Were Three is more of a whodunit story, that is, about discovering the murderer, the kind of story that, apparently, Mainwaring himself eventually grew bored of. In this case, the investigator is journalist Robin Bishop, assisted by detective Humphrey Campbell, always in the background but effective.

In Los Pinos, California, a young outsider from a wealthy family, fleeing a semi-arranged marriage, is murdered. The case strangely seems to be connected to the disappearance of a Great Dane, owned by another wealthy local resident. Later, they also kill the young woman's father… and then there were three.