This story starts one year after the end of the third book, in the early fourteenth century. The monastery of St Alcuin's is settling down and adjusting to its new abbot, who is taking the place of Father Peregrine, when an old enemy, Prior William, arrives seeking refuge. Reluctantly taking in the man who so ill-treated their much loved former leader, the upended community must address old fears and bitterness while warily seeking reconciliation. But will William the refugee spread poison, or receive healing? In her fourth book in the series, Penelope Wilcock wrestles with the difficulties of forgiveness and the cautions of building trust. What is truly the hardest thing to do?