The Turkish island of Heybeliada is home to a strange community. Its buildings are protected by gates and guns, while its inhabitants have new identities bestowed upon them – meaningless names plucked from the telephone directory. This weird settlement is called Portmantle and is “a sanatorium of sorts” though its people are not sick. Instead they are artists with “depleted minds”. Each painter, poet and playwright within the high gates has been nominated for membership by a sponsor who’s certain the wilting artist will flourish if they can only be free to “work outside the straitjacket of the world and its pressures”.

Elspeth Conroy, awarded the name of ‘Knell’ on arrival, is a Scottish artist who has retreated to Portmantle to work on a magnificent mural, titled The Ecliptic, which has baffled and tormented her. On the island, freed from the humdrum duties of paying bills and buying food, she hopes for inspiration, and she begins to find it upon discovering mushrooms in the woods behind her cabin which emit a nocturnal blue glow, “like the antiseptic liquid barbers keep their combs in”. She harvests the mushrooms, powdering them into an astonishing blue pigment which revives her urge to paint. But any hope of concentration is broken with a new arrival at Portmantle, a disturbed teenage boy known as Fullerton.

Strangely for a character of such vibrant occupation, and in such an odd setting, Elspeth has no discernible voice. She narrates the novel, yet could be anyone, of any gender or age. Benjamin Woods adds to her character with a frill of details to prove she is indeed an artist, dotting her dialogue with terms like ‘diptych’, ‘muller’ and ‘gouache’ but these words are mere tags and no compensation for thin characterisation.

What does compensate is the author’s skill in evoking place and atmosphere. He is excellent at the exotic, humid, enclosed feel of Portmantle. Its landscape is luscious with pomegranate trees, dwarf oaks, glowing mushrooms and rainfall, all surrounded by the blue Sea of Marmara, “fathomless, agleam”. This sense of place is powerful, even oppressive, and ornate Turkish words pepper these chapters – ‘kokorec’, ‘salep’, ‘Cam Limani Yolu’ – adding to the luxuriant flavours and textures.

However, the author almost sabotages his skilful portrayal of Portmantle as a mysterious, secluded enclave by having his main characters, all British, constantly visit one another for gossip and backgammon. They bicker about the arrival of new people, whom they sneeringly refer to as ‘short-termers’, grumbling if they sit at their table in the dining hall. “Crikey!” one of them declares. “This place is going to ruin!” The aim may have been the portrayal of an aloof artistic clique, but it often threatens to tip the novel into a satire of Brits abroad.

Yet the clique cannot ignore Fullerton, the new boy. They are asked to befriend him as he suffers from vicious nightmares and dangerous sleep-walking, but when his disturbed behaviour provokes a horrific incident, Elspeth decides she must leave Portmantle and, at this point, the novel begins to flag.

When Elspeth leaves, there begins a lengthy, plodding flashback section depicting her growth as an artist. Here the story falters because we’ve suddenly exchanged the exotic for the pedestrian, entering a conventional narrative peopled by clichéd characters, such as the aristocratic art critic Wilfred Searle, the unwashed artist Jim Culvers, and the kindly old tutor whose advice was the awfully tepid “paint what you believe”. This section is too long and meandering and leaves the novel with a niggling feeling of unevenness, so that when we finally return to Portmantle it’s with an unsatisfying sense that we’re simply hurrying the plot to its conclusion – a conclusion some may find infuriating.

Thankfully, this saggy middle-section is buttressed on both sides by the peculiar and enticing world of Portmantle, where the writing is vigorous and confident. Indeed, this sense of something being enclosed or merged is repeated throughout the book. The novel itself incorporates a variety of styles: satire, light comedy, literary thriller and a conventional story about an artist’s evolution, all merging to create the whole. Likewise, the themes have the same sense of overlap: love merges with obsession, creativity might shade into genius, reality can fade into dream. This is an ambitious literary thriller reaching for some bold themes out on the weird island, but the author was too determined to keep one foot on dry land.