The peaceful existence of three eccentric, secluded nuns living in a remote island monastery is shattered when a priest unwittingly happens upon them.

As Frankie launches a search for her missing brother, the nuns give Ignatius an ultimatum: wed himself to their order or face certain death.

A lifetime of lies drives a wedge between Carla and her sisters. Iphigenia is forced to face her past in order to save her home, and Ignatius must decide where his loyalties lie.

As a memorial is held for Ignatius on the mainland, Father Bob arrives on the island to annihilate the Sisters of St. Agnes. Iphigenia's loyalty is tested when she considers a deal with the devil to save the monastery. Series final.