The Going Down of the Sun by Jo Bannister

might be.
    So he’d left his little surprise, and left the boat yard either unnoticed or unremarked, and collected his wages and vanished back into the underworld whence he came. And Alison motored the Skara Sun down to Crinan to meet her lover, and on their second morning together the bomb went off or the seal leaked or the doctored cylinder was connected and Alison struck the fatal match.
    However the explosion was triggered, there was clearly a delay mechanism, to ensure they were both aboard before it happened. McAllister wanted them both dead. But sheer luck had put Curragh on deck at the critical moment, and another mammoth slice of fortune had put Harry and I close enough to help when the sea would otherwise have finished what the explosion began.
    McAllister must have been furious to learn Curragh had escaped. But he thought quickly—all the indications were that he was a quick-thinking man—and found another way of exacting payment for the wrong he had suffered. Next best thing to having his wife and his wife’s lover dead together at the bottom of Loch Sween was seeing Curragh rot his life away in Barlinnie Prison for a murder he didn’t commit.
    So as soon as the news came through he was at the hospital with his tale of Alison’s bequest and his accusation, knowing that however wild it sounded, the police would have to investigate. The man who’d fixed the boat, or another like him, could fix him up with enough evidence to see the boy condemned. He’d still have achieved what he set out to, revenged on and rid of the wife who had cheated and the man who had cuckolded him, free to enjoy his wealth and his power and his son without—
    Without, I thought then with the sudden grasp of a revelation, the risk of losing the child. That’s why he needed Alison dead. Cutting her off without a penny wouldn’t suffice: if she wanted to take the baby, custody was unlikely to be awarded to McAllister. “I can look after both of you,” Curragh had said. He certainly wasn’t referring to the sturdy Glaswegian. He wanted Alison to leave her husband and bring her baby and come to him.
    McAllister was a man in his fifties, a rich man but a cripple. It had taken him until now to produce an heir. He must be aware that this baby might be the only one he’d ever have. A man like McAllister would not lie down while the courts took his son and heir from him. A man like McAllister would do what he had to in order to preserve his succession. He could even have done it still loving his wife.
    Harry said, in the patient voice of a man repeating himself for the third time, “I said, Are you ready for lunch yet?”
    My mind returned to the hotel room by degrees. For a few moments my eyes actually saw him blurred, standing in the doorway like a faintly woolly column of grey and white, rather than a middle-aged policeman in flannels and an Aran sweater wishing his wife had let him bring his suit on holiday.
    I blinked and the woolliness dispersed. “What?—Sorry?”
    He frowned. “Are you all right?”
    â€œYes, of course,” I said. “Or rather, no. I’ve been thinking.”
    â€œOh God,” he groaned, “not again?” There was real pain in his eyes, as if I’d confessed to some dreadful vice he’d thought me cured of. “What have you come up with this time?”
    So I told him, in a certain amount of detail—I seem to remember a glazed expression creeping over his face and halfway through he sat down on the bed to take the weight off his feet. But he listened without interruption until I had finished, which was as much as I had a right and more than I had reason to expect.
    Then he looked down one side of his unshapely nose at me, a look in which I recognised affection and amusement and a tolerant disbelief at what he was married to. “That’s it?”
    I was a shade taken aback.