Discuss why and how profound isolation affects nearly all the characters in this story

The isolation Matt and Ruth experience is a result of their son Frank's murder.  When a person is isolated, he or she is apart from others.  Though Matt has friends, like Willis, Willis has not been through what Matt has been through.  Willis can be (and is) sympathetic to Matt's situation and can help him with enacting revenge, but he will never be in the same place Matt is, psychologically. Ruth also has no peers that can really be with her in her grief, and in the end, she must keep Matt and Willis's  secret—something else that sets her apart from others. Ruth and Matt are even isolated from one another because each has to deal with their grief on their own.
Richard Strout, Frank's murderer, is also a character that experiences isolation.  When he and Mary Ann divorce, he lives apart from her and their children.  Mary Ann moves on with her life and develops a relationship with Frank. Richard Strout is alone, isolated from his family, and jealous of Mary Ann and Frank's relationship.  After Frank's murder, Strout becomes a pariah while he is out on bail.  And ultimately, when he faces his death at the hands of Matt and Willis because of the ruinous choices he has made, Strout is alone.