The narrative covers a 13 day period in June 2011
Icelander Olaf  flies into Gatwich where his erratic behaviour leads to immediate arrest as a suspected terrorist. Sectioned and sent to a psychiatric unit he finds himself in the care of Irish psychiatrist Patricia Carragh  In the aftermath of an acrimonious divorce she is struggling to cope with an excessive caseload, a disturbed teenage son Colm  and estrangement from daughter Caitlin .
Patricia unearths Olaf's history of traumatic loss including the death of his father in childhood, and the unexplained disappearance of his young son. Olaf appears steeped in esoteric wisdom, professes profound spiritual beliefs but lays claim to supernatural gifts and powers which strike Patricia as probably illusory. He insists his trip to England is to fulfil a sacred quest by climbing Scafell on midsummer night.
Olaf becomes attracted to another of Patricia's patients Morgana , who is in a vulnerable state following disturbing experiences at the hands of a notorious religious cult. Convinced that for all his unorthodox beliefs and actions Olaf represent no danger to himself or others, Patricia is ready to discharge him. The security services, however, are not sure about him and Olaf is placed in the relative freedom of a 'half way house'.
Patricia takes Colm to Ireland to see her mother who has cancer and also grandmother Frances. Learning of Colm's condition, Frances advises a visit to the legendary Ben Bulben for him to perform a simple ritual. Against her better judgement Patricia agrees; to her surprise the effect on Colm is positive. Returning to England she asks Olaf to help her with research into psychic experiences and discovers his growing relationship with Morgana may result in him abandoning his plans for midsummer night. Without undestanding why Patricia is concerned about this possibility.
Working with Olaf coincides with a series of positive changes in Patricia's attitude to and experience of life. She becomes more assertive with her controlling medical director and finds the courage to resist attempts by her ex-husband to pressure her into making financial sacrifices which would benefit him but not her.
Unforeseen circumstances bring her to Canterbury cathedral and later to a 2,500 year old yew tree - on both occasions in Olaf's company. Both experience culminate in experiences which she cannot explain on an intellectual level, but leave her feeling better able to deal with the challenges she faces in life. They also convince her that Olaf's Scafell visit is somehow linked to the emotional healing of his traumas.
Patricia continues to enage with Olaf on the pretext of carrying out further research, but she is also motivated by a feeling of responsibility to ensure he completes the midsummer quest on Scafell. Olaf who has moved in with Morgana is clearly resistant, becoming angry with Patricia because of her efforts to influence him.
Deciding she must trust to fate, Patricia is surprised to find Olaf on her doorstep the night before midsummer asking her to cancel her appointments and drive him to Scafell. Colm begs to accompany them, and it is he who witnesses and relates to Patricia a mysterious encounter between Olaf and a child on the misty mountain.
In the epilogue we learn while Colm remains fascinated by the enigmatic Olaf, Patricia rejects the experience because it challenges her rational view of the world.