AS SHE lay on the divan in her flat in Queen's Gate, Caroline Rose suddenly heard the sound of a typewriter. Tap-tappity-tap. It seemed to come through the wall on her left. It stopped, and was immediately followed by a voice remarking her own thoughts. It said: On the whole she did not think there would be any difficulty with Helena. Caroline, on another plane of existence, was Muriel Spark. She was trying to scrape a living by writing in London in the mid-1950s, divorced, with a small son. Coffee and diet pills kept her going, but also gave her hallucinations. Because “if you're going to do a thing, you should do it thoroughly”, she had converted in 1954 from vague Christianity to Roman Catholicism. God loomed large in Ms Spark's dark, biting, witty novels. In the early years of her career it was the vogue for Catholic converts to be obsessed with Him, sin, and themselves. But unlike Evelyn Waugh, who warmly praised her, or Graham Greene, who kept her going with a monthly allowance and cases of wine, Ms Spark preferred to leave aside the heavier, guilt-ridden aspects of the faith. Her newly-made Catholics were comic and somewhat tentative. They did not agonise much. But, like her, they were perplexed that a divine Creator should allow evil in the world, and especially intrigued by the permutations of free will and fate. Dabblings on the dark side held a particular fascination. “The Ballad of Peckham Rye” (1960) satirised Satanism in south London, while “The Bachelors” (1960) anatomised spiritualism in Victoria. (“The Interior Spiral...That's a make of mattress, isn't it?”) Her light touch still managed to carry maximum disapproval. A phrase, too, could pin down more or less anything she spotted. “The evening paper rattle-snaked its way through the letter box and there was suddenly a six-o'clock feeling in the house.” “She yawned with her mouth all over her face.” Bathos was a speciality: “Human nature is apt to fail in spite of regular prayer and deep breathing”. By birth and childhood formation Ms Spark was a Scottish writer, and always acknowledged it. Like freckles, as she said, her Scottishness could never be lost, though in her later Italian exile she revelled at being European. She wrote of Edinburgh with a child's intensity: the “amazingly terrible” smells of the Old Town, the sight of the unemployed fighting, spitting and cursing, but also the way it might become “a floating city when the light was a special pearly white”. Her own neighbourhood, Bruntsfield, was middle-class, and her parents Jewish-Episcopalian. But she became gradually aware of the Calvinism around her, symbolised by the frightening blackened stone of the city's churches. The God of Calvin, as she wrote in “The Prime of Miss Jean Brodie”, her small autobiographical masterpiece of Edinburgh public-school life, “sees the beginning and the end”. Nunnishness, it might be thought, figured little in Ms Spark's real life. Instead there was fame, many prizes (though she missed out on the Booker, the biggest British fiction award), sleek clothes, and a fortune that drove her abroad to escape the taxman. Yet she lived for 27 years in a converted 13th-century church in Tuscany, happily eschewing the literary whirl, writing longhand in spiral-bound notebooks that were sent to her from Edinburgh. And she died in the Easter season, the best time for Catholics, in a way that might almost have been planned. Tap-tappity-tap.