What is the summary of Matthew Arnold's poem, "The Forsaken Merman"?

Mathew Arnold was greatly disturbed by the loss of religious faith as a result of the advance of scientific spirit. 'The Forsaken Merman' is pervaded with a deep note of sadness. It has a haunting charm because of its thought and music. No wonder it has been regarded as a great poem. The title of the poem is significant. The 'wild white horses' signifies the huge white waves indicating a coming storm while the 'champ and the chafe'signifies the hiss and foam at the mouth of the shore.
The merman (a fabulous creature- half man and half fish) is forsaken or deserted by the woman who had married him, had children by him, and enjoyed all the comforts and luxury of his submarine home. She had been a good mother and a good wife but one day when she had heard the church bell ring, she felt restless and said that she must go and join her kinsfolk, for otherwise she would lose her soul. The 'easter-time is the time of the Christian Festival commemorating Christ Ressurection. She left to say her prayers in the church. The sound of the church bell was heard till the cave where they dwelt. The wet mud of the sea feeds the hungry shores of the dry land.
The merman along with their children waited on the sea-shore, then went up to the church, saw her there, but she would not come back to join them. Now the merman and his children are once again on the sea-shore with the fond hope that she will come and join them. But that is a hope never to be realized. The poet makes the forlorn merman imagine the kind of life that she is living with her kinsfolk. She is happy but from time to time sighs from sorrow remembering her children. The merman's final thought is that the loved lady spending her days in the town away from those who loved him is a heartless one ('There dwells a love one/ But cruel is she).

Arnold has infused deep human feelings into the poem.The metrical flow of the verse hauntingly suggests the emotions of love , disillusionment and frustration. There is a mournful note that informs the whole poem. The woman's desertion is like the desertion of faith. Life the Victorian man lamenting the disappearance of religious faith, the merman laments his wife's faithlessness.