Three Major Themes in the Play:
First, there is the theme of sin and expiation and atonement for that sin through suffering. Secondly, there is the theme of the oneness of time, the continuity of the past, the present, and the future, a theme which constantly recurs in the works of Eliot. Thirdly, there is the theme of spiritual loneliness and isolation and the difficulty of communicating these spiritual states. The three themes have been closely interrelated and merged and fused.
The Central Theme of Sin and Expiation:
The central theme of the play is the theme of sin and expiation. Harry, Lord Monchensey kills his wife (or at least he imagines that he has killed her) by throwing her over the rails into the sea. Ever since he has suffered from a haunting sense of guilt and has not known even a moment's rest or peace of mind either by day or night. He is ever conscious of being followed or pursued. He feels that certain unknown eyes ever watch him and pursue him. He returns to Wishwood in the hope of escaping the eyes, and finding some rest and mental peace there. But the eyes, the Furies, the goddesses of revenge, pursue him here also. Through Agatha, his spiritual mother and guardian, he comes to know of the real nature of his sin. It is an inherited sin and not his sin alone. His father had made various attempts at killing his mother when she was with child with him. It was Agatha who saved the life of his mother, and his own life. Harry now realises that the family is under a curse, and he must suffer and expiate, and thus redeem his family. He is tempted by Mary to love and marry her and lead a comfortable life on the material plane. But Harry elects to suffer and expiate. However, we must acknowledge that this choice is made without - any inner - conflict. We are not given any idea of Harry's struggle to overcome the temptation that is offered to him, a struggle which always precedes any crucial decision. This absence of conflict weakens the dramatic effectiveness of Harry's choice.
The Theme of the Continuity of Time, the Oneness of the Past and the Present:
Closely integrated with this theme of sin and expiation is the theme of the continuity of time , the oneness of the past and the present . Time is a continuous flow and the division of time into the past and the present is artificial. The present is the moment of interaction of the past and the future. The present is determined by the past, and the future is constantly with us in the present in the form of our hopes and aspirations. Amy tries to obliterate the past, but to no avail. During Harry's absence for eight long years nothing is changed in the home. Everything is at the same place. Nothing is moved and shifted. The uncles and aunts are directed to behave as if nothing had happened, and nothing had changed. But Harry is altogether a changed man. He committed the crime eight years ago, but he suffers for it deep spiritual anguish in the present also. Moreover, his own crime is but a repetition of the crime of his father in wishing to kill his mother. Even since the family has been under a curse, and he must suffer and expiate in the present and thus redeem his family from that curse, so that the crime is not repeated in the future, and future suffering is avoided.
The Theme of Isolation and Spiritual Loneliness:
The theme of the sense of isolation and the impossibility of communications is quite recurrent in Eliot's works; The Family Reunion is no exception to this. It treats the hero as a bird sent flying through the purgatorial flame. This theme of the essential loneliness of the individual is revealed even amidst the family-gathering is a forced or laboured idea. They are all prepared voices, not individuals who know each other in the family set - up. It is just like the theatre; a make believe world cut out of darkness by judicious prearrangement of spot-lights, in which all appearance and reality far beyond our power of comprehension. It begins as a kind of make-believe and make-believing makes it real. Harry cannot express his mysterious situation either by speech or action. Harry thus strikes us by his similarity to Hamlet.
Like Hamlet, he too is conscious of the cursed spite of destiny that brought him into the midst of times which are out of joint but he is not convinced that he was born to set it right. The actual action of the play is the realization of Harry that he is the conscience of his unhappy family and how he dedicated himself to expiate the sins of his family and save himself and others.
His exit begins another story of martyrdom. In this respect the play can be said to deal with the Christian doctrine of the atonement and the mysterious exchange of sin and suffering in the spiritual world through which mankind partakes in that mystery.