Although he knew sleep would not come easily, he swallowed the last dregs of his nightly scotch and dragged himself up the stairs to join his wife, who had decided to have an early night. Sleep often eluded him these days. Instead, he found his mind invariably turned to try to identify what it was that overshadowed his life. Ever present but also elusive, he knew he had to pin it down and deal with whatever was troubling him before he could find peace.

He found his wife sitting up and reading her kindle, which she put down as he slipped into bed beside her. They'd recently celebrated their golden wedding anniversary by getting identical tattoos. She knew he was troubled and helped in her own way when...