There's something sweet and sad about ill-fated love affairs.

Such is the premise of Orkney, the second novel of John Llewellyn Rhys prize winner Amy Sackville, who also wrote The Still Point. A university professor and his ex-student elope after a year of secret encounters. The young but bizarrely white-haired bride and her older groom head to her birthplace on Orkney. While on honeymoon, the couple become affected by the girl's personal issues: memories of her sea-faring father who abandoned her, and the girl's own obsession with the ocean, even though she can't swim.

The blustery sea provides an appropriate backdrop to this brooding novel. Sackville writes in the voice of the mournful groom, Richard. He's kind but fretful, thinking constantly of their age difference and resolving: "I will simply refuse to grow old." He's protective of his new partner and his inclination to refer to her as "my young wife" means we never actually learn her name. But perhaps her name is not that important. A Tennyson scholar finishing his latest book, he likens her to the poet's Vivien while he is Merlin, the magician who "teaches her everything he knows" and harbours for her "a possessive love".

Theirs is an odd relationship, not because of their 40-year age difference but because of their rather vapid personalities. He is dumbfounded by her beauty and her interest in him; she relies on him as a father figure, reaching for him after her dreams of drowning. Mythology of the sea is one way in which they communicate. Sipping whisky by the fire, she tells him Orcadian tales of selkies. One story describes a silver-haired selkie who, while in female form, has her sealskin stolen by a crofter. He tricks the mythical creature into marrying him. When Richard comments that it's a sad story, the girl counters: "He got 20 years out of her." This leaves the new groom worried.

Sackville aims for a novel filled with folklore and romance. In the beginning, the language is intelligent and evocative. Images of ferry boats, rock pools and blankets create a sense of safety. Generous application of commas and a sparing use of quotation marks create a lilting, flowing narrative suggestive of sea rhythms. But the initial magic dissipates. Sackville repeats the same day over again: the couple wake up to tea and toast, he writes his book and she wanders along the shore, then at night she dreams of perishing in the ocean. The girl's enactment of her past issues and Richard's worries about their future becomes an unsolvable and all-too-familiar refrain.

That said, the novel closes with a jolt. One half of the couple mysteriously disappears. In a clever way, Sackville becomes inventive with the appearance of the text. Fragmented sentences describe the character's abrupt departure. Gaps of white space on the page evoke the left-behind spouse's sense of abandonment. At this time the point of Orkney emerges: this is a story not about love, but about power.