How many people can a person love? On the final day of their honeymoon in San Francisco, where they've just had their first threesome, John and Beth Hempel board a plane in awkward silence, headed for their new home in Bozeman, Montana. Also in Bozeman: Beth's best friend, the stoic, carefree Rebekah Fleckman, with whom both John and Beth are in love. As John and Beth's marriage gets off to a rocky start haunted by past tragedies and present...